launcher: one Launch button, driven by an explicit launch state machine

The launcher used to make the user perform OpenFUT's internal launch order by
hand — Start LSX, Start autopatch, Run pre-launch checks, "Arm client", then a
button called *Start Services & Launch Game*. Those are implementation details
of how FIFA 17 is persuaded to talk to OpenFUT, and getting the order wrong
produced failures that surfaced much later as "the game crashed": autopatch
started before ptrace_scope is 0 silently patches nothing at all.

The normal flow is now: open the launcher, read one status card, press
**Launch FIFA 17**.

New `launch` module holds the sequence as a state machine (Phase: Idle,
Checking, PreparingClient, StartingServices, Validating, Launching, Running,
Failed) and runs it on a worker thread, so the UI thread never blocks on a
socket, a Polkit prompt or a process spawn. The UI renders that state; it does
not coordinate services.

Every step asks what is already true before acting:

  - a healthy service is reused, never restarted;
  - client preparation is skipped when the checks it would repair already pass,
    which also avoids a pointless password prompt;
  - the hook config is reconciled from the current settings.

It stops at the first failed step and never starts FIFA into a client it knows
is broken. Preparation deliberately runs BEFORE autopatch, against the order in
the brief, because autopatch cannot write FIFA's memory until arming has set
ptrace_scope and would otherwise "succeed" while doing nothing.

Ownership is now tracked, which the old model could not express: it only knew
about children it had spawned, so a service started by hand for a debugging
session read as "stopped" and starting it again just collided on the port.
`ServiceSupervisor` observes our own child first, then scans /proc for a foreign
instance, and reports `ServiceRuntime { running, started_by_launcher, pid,
detail }`. `stop_permitted` refuses to kill anything the launcher did not start,
under any cleanup policy. `CleanupPolicy` states the shipped behaviour — leave
launcher-started services running for the next launch — instead of leaving it to
chance, and the FIFA-exit path goes through it.

Readiness comes from observation, never from a button press: LSX is ready only
when the port FIFA dials is actually held, and "we have not looked" renders as
"Not checked yet", never as green.

Manual controls all survive under **Advanced / Diagnostics** — per-service
start/stop/restart with PIDs and ownership, "Prepare client" (the old "Arm
client", renamed; internals still say arm), "Run pre-launch checks", "View
logs", and a new "Launch game only" escape hatch for debugging a launch the
sequence refuses.

Tests: 73 pass (15 new). Sequencing and ownership are unit-tested through a
`LaunchOps` fake, so "don't launch after a failed step", "don't restart healthy
services" and "don't kill what we didn't start" hold without a FIFA install, a
Polkit agent or root.

Exercised live under Xvfb: the card shows four observed rows and one button; a
launch stopped at LSX with "127.0.0.1:4216 is held by an unrelated process",
listed every step's verdict, and did NOT start the game; Advanced showed a real
pre-existing autopatch as "Running (foreign) · pid 382382 · started outside this
launcher" with Stop/Restart disabled.

src/local_services.rs

@@ -29,6 +29,10 @@ use crate::fifa17_capability::{
 };
 use crate::logs::LogBuffer;
 
+/// The loopback endpoint LSX must own. FIFA dials this exact address and nothing
+/// else, so "is LSX ready?" is answerable without asking LSX anything.
+pub const LSX_ADDR: SocketAddr = SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::LOCALHOST, 4216));
+
 #[derive(Debug, PartialEq, Eq)]
 struct CommandParts {
     program: String,
@@ -36,7 +40,7 @@ struct CommandParts {
 }
 
 /// Which companion service. The `str` values are used in log prefixes.
-#[derive(Copy, Clone, PartialEq, Eq)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum Service {
     /// LSX Origin/EADesktop emulator — binds loopback 4216, unprivileged.
     Lsx,
@@ -179,6 +183,11 @@ impl ManagedService {
         self.stopping.is_some()
     }
 
+    /// PID of the child this launcher owns, if it owns one.
+    pub fn pid(&self) -> Option<u32> {
+        self.child.as_ref().map(Child::id)
+    }
+
     /// Begin stopping the service without waiting on the egui UI thread.
     pub fn stop(&mut self, log: &Arc<Mutex<LogBuffer>>, service: Service) {
         if self.stopping.is_some() {
@@ -219,6 +228,235 @@ pub struct CapabilityWiring {
     pub sink: Arc<Mutex<Fifa17ClientCapabilities>>,
 }
 
+/// What is actually true about one companion service right now.
+///
+/// Deliberately observed, never remembered: a button press is not evidence that
+/// a service is up, and a service that died on its own must not keep showing
+/// green because the launcher once started it successfully.
+#[derive(Debug, Clone, PartialEq, Eq, Default)]
+pub struct ServiceRuntime {
+    pub running: bool,
+    /// True only while THIS launcher owns the live process. Decides whether
+    /// cleanup is allowed to touch it: a service someone started by hand for a
+    /// debugging session must survive a launch/exit cycle.
+    pub started_by_launcher: bool,
+    pub pid: Option<u32>,
+    /// Observed supporting detail for the Advanced panel. Only ever facts the
+    /// launcher actually established.
+    pub detail: Option<String>,
+}
+
+impl ServiceRuntime {
+    /// Whether this service is usable for a launch, as opposed to merely alive.
+    /// For LSX that means the port FIFA dials is genuinely held.
+    pub fn ready(&self) -> bool {
+        self.running
+    }
+}
+
+/// True when something holds LSX's fixed loopback port.
+pub fn lsx_port_busy() -> bool {
+    match TcpListener::bind(LSX_ADDR) {
+        Err(error) => error.kind() == std::io::ErrorKind::AddrInUse,
+        Ok(listener) => {
+            drop(listener);
+            false
+        }
+    }
+}
+
+/// PID of a process running `service`'s responder script that this launcher does
+/// not own, if there is one.
+///
+/// Scans `/proc` — no extra dependency, no privilege, and no guessing: a service
+/// left running by a previous launcher instance or started by hand from a shell
+/// is a real state the UI has to be able to report, and cleanup has to respect.
+pub fn foreign_pid(service: Service, ours: Option<u32>) -> Option<u32> {
+    let script = service.script();
+    let self_pid = std::process::id();
+    let entries = std::fs::read_dir("/proc").ok()?;
+    for entry in entries.flatten() {
+        let Ok(pid) = entry.file_name().to_string_lossy().parse::<u32>() else {
+            continue;
+        };
+        if pid == self_pid || Some(pid) == ours {
+            continue;
+        }
+        let Ok(cmdline) = std::fs::read(entry.path().join("cmdline")) else {
+            continue;
+        };
+        if cmdline
+            .split(|b| *b == 0)
+            .any(|arg| String::from_utf8_lossy(arg).ends_with(script))
+        {
+            return Some(pid);
+        }
+    }
+    None
+}
+
+/// Whether a stop request may touch this service.
+///
+/// Pure, so the ownership rule is testable without a process: refusing to kill
+/// something the launcher did not start is the whole reason ownership is tracked,
+/// and it must not depend on what happens to be running on the test machine.
+pub fn stop_permitted(runtime: &ServiceRuntime, label: &str) -> Result<(), String> {
+    if runtime.running && !runtime.started_by_launcher {
+        return Err(format!(
+            "{label} was started outside this launcher{} — stop it where it was started.",
+            match runtime.pid {
+                Some(pid) => format!(" (pid {pid})"),
+                None => String::new(),
+            }
+        ));
+    }
+    Ok(())
+}
+
+/// Owns both companion services and answers "what is running, and who started
+/// it?" for the whole launcher.
+///
+/// Exists so the launch sequence and the Advanced panel act on the same objects.
+/// Two independent copies of that state is how a UI ends up claiming Ready while
+/// the process is dead.
+pub struct ServiceSupervisor {
+    lsx: ManagedService,
+    autopatch: ManagedService,
+    log: Arc<Mutex<LogBuffer>>,
+}
+
+/// Whether [`ServiceSupervisor::ensure_running`] had to do anything.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Ensured {
+    /// Already up — left strictly alone.
+    Reused,
+    Started,
+}
+
+impl ServiceSupervisor {
+    pub fn new(log: Arc<Mutex<LogBuffer>>) -> Self {
+        Self {
+            lsx: ManagedService::default(),
+            autopatch: ManagedService::default(),
+            log,
+        }
+    }
+
+    fn slot(&mut self, service: Service) -> &mut ManagedService {
+        match service {
+            Service::Lsx => &mut self.lsx,
+            Service::Autopatch => &mut self.autopatch,
+        }
+    }
+
+    /// Observe one service: our own child first, then any foreign instance.
+    pub fn observe(&mut self, service: Service) -> ServiceRuntime {
+        let log = Arc::clone(&self.log);
+        let slot = self.slot(service);
+        if slot.stopping() {
+            return ServiceRuntime {
+                running: true,
+                started_by_launcher: true,
+                pid: None,
+                detail: Some("stopping".into()),
+            };
+        }
+        let ours = slot.pid();
+        if slot.running(&log, service.label()) {
+            let mut runtime = ServiceRuntime {
+                running: true,
+                started_by_launcher: true,
+                pid: ours,
+                detail: None,
+            };
+            if service == Service::Lsx {
+                runtime.detail = Some(if lsx_port_busy() {
+                    format!("holding {LSX_ADDR}")
+                } else {
+                    // Alive but not listening: real, and not "ready".
+                    runtime.running = false;
+                    format!("process alive but {LSX_ADDR} is not held")
+                });
+            }
+            return runtime;
+        }
+
+        match foreign_pid(service, ours) {
+            Some(pid) => ServiceRuntime {
+                running: true,
+                started_by_launcher: false,
+                pid: Some(pid),
+                detail: Some("started outside this launcher".into()),
+            },
+            None if service == Service::Lsx && lsx_port_busy() => ServiceRuntime {
+                running: false,
+                started_by_launcher: false,
+                pid: None,
+                detail: Some(format!("{LSX_ADDR} is held by an unrelated process")),
+            },
+            None => ServiceRuntime::default(),
+        }
+    }
+
+    /// Start `service` only if it is not already usable. Never restarts a healthy
+    /// service, and never adopts a foreign one as ours.
+    pub fn ensure_running(&mut self, service: Service, spec: SpawnSpec) -> Result<Ensured, String> {
+        let runtime = self.observe(service);
+        if runtime.ready() {
+            self.log.lock().push(format!(
+                "[launcher] {} already running{} — reusing it.",
+                service.label(),
+                match runtime.pid {
+                    Some(pid) => format!(" (pid {pid})"),
+                    None => String::new(),
+                }
+            ));
+            return Ok(Ensured::Reused);
+        }
+        if let Some(detail) = runtime.detail.filter(|_| !runtime.running) {
+            // No service-name prefix: every caller already renders the service it
+            // asked about, and the launch card would print "LSX: LSX: …".
+            return Err(detail);
+        }
+        let child = spawn(
+            service,
+            &spec.python,
+            &spec.tools_dir,
+            spec.persona_id,
+            &spec.persona_name,
+            spec.capability,
+            Arc::clone(&self.log),
+        )
+        .map_err(|e| e.to_string())?;
+        *self.slot(service) = ManagedService::from_child(child);
+        Ok(Ensured::Started)
+    }
+
+    /// Stop a service the launcher owns. A foreign process is reported, never
+    /// killed: the launcher did not start it and does not know who needs it.
+    pub fn stop(&mut self, service: Service) -> Result<(), String> {
+        let runtime = self.observe(service);
+        stop_permitted(&runtime, service.label())?;
+        let log = Arc::clone(&self.log);
+        self.slot(service).stop(&log, service);
+        Ok(())
+    }
+
+    pub fn stopping(&mut self, service: Service) -> bool {
+        self.slot(service).stopping()
+    }
+}
+
+/// Everything [`spawn`] needs, bundled so the launch sequence can hand it over
+/// as one value per service.
+pub struct SpawnSpec {
+    pub python: String,
+    pub tools_dir: String,
+    pub persona_id: u64,
+    pub persona_name: String,
+    pub capability: Option<CapabilityWiring>,
+}
+
 /// Spawn a companion service. `python` is the interpreter, `tools_dir` the
 /// directory holding the responder scripts. Streams stdout+stderr into `log`.
 /// Returns an error (without spawning) if the tools dir or script is missing.
@@ -350,7 +588,7 @@ pub fn spawn(
     }
 
     if service == Service::Lsx {
-        let address = SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::LOCALHOST, 4216));
+        let address = LSX_ADDR;
         if let Err(error) = wait_for_listener_ready(&mut child, address, Duration::from_secs(3)) {
             let _ = child.kill();
             let _ = child.wait();
@@ -418,4 +656,89 @@ mod tests {
             .expect_err("exited child must not be reported ready");
         assert!(error.to_string().contains("exited before becoming ready"));
     }
+
+    fn supervisor() -> ServiceSupervisor {
+        ServiceSupervisor::new(Arc::new(Mutex::new(LogBuffer::new())))
+    }
+
+    #[test]
+    fn a_service_this_launcher_never_started_is_never_reported_as_ours() {
+        // The old model only knew about children it spawned, so it could not tell
+        // "stopped" from "running, but not mine". Note this box may genuinely have
+        // a foreign responder running — that is a real observation, and the
+        // invariant is about ownership, not about it being absent.
+        let mut sup = supervisor();
+        let runtime = sup.observe(Service::Autopatch);
+        assert!(
+            !runtime.started_by_launcher,
+            "nothing was spawned here, so nothing may claim launcher ownership"
+        );
+    }
+
+    #[test]
+    fn a_launcher_owned_child_is_observed_as_ours_and_reaped_when_it_dies() {
+        let mut sup = supervisor();
+        let child = Command::new("sh")
+            .args(["-c", "sleep 30"])
+            .spawn()
+            .expect("spawn long-lived child");
+        let pid = child.id();
+        sup.autopatch = ManagedService::from_child(child);
+
+        let runtime = sup.observe(Service::Autopatch);
+        assert!(runtime.running);
+        assert!(runtime.started_by_launcher, "we spawned it");
+        assert_eq!(runtime.pid, Some(pid));
+
+        // Stopping is allowed precisely because it is ours.
+        sup.stop(Service::Autopatch).expect("ours to stop");
+    }
+
+    #[test]
+    fn stopping_a_foreign_service_is_refused_rather_than_killing_it() {
+        // A service someone started by hand for a debugging session must survive a
+        // launch/exit cycle, and the refusal has to say where to stop it. Asserted
+        // on the pure rule so it holds regardless of what this machine is running.
+        let foreign = ServiceRuntime {
+            running: true,
+            started_by_launcher: false,
+            pid: Some(4242),
+            detail: None,
+        };
+        let error = stop_permitted(&foreign, "autopatch").unwrap_err();
+        assert!(error.contains("started outside this launcher"), "{error}");
+        assert!(error.contains("4242"), "{error}");
+
+        let ours = ServiceRuntime {
+            running: true,
+            started_by_launcher: true,
+            pid: Some(99),
+            detail: None,
+        };
+        assert!(stop_permitted(&ours, "autopatch").is_ok());
+        // Stopping something that is not running is a harmless no-op.
+        assert!(stop_permitted(&ServiceRuntime::default(), "autopatch").is_ok());
+
+        assert!(
+            crate::launch::services_to_stop(
+                crate::launch::CleanupPolicy {
+                    stop_launcher_started_services: true,
+                },
+                &[(Service::Autopatch, foreign)],
+            )
+            .is_empty(),
+            "a foreign service is never in the stop list"
+        );
+    }
+
+    #[test]
+    fn foreign_pid_ignores_the_launcher_process_itself() {
+        // The scan matches on the responder script name; this process is not one,
+        // and must never be reported as a service.
+        assert_ne!(foreign_pid(Service::Lsx, None), Some(std::process::id()));
+        assert_ne!(
+            foreign_pid(Service::Autopatch, None),
+            Some(std::process::id())
+        );
+    }
 }