refactor: apply CLAUDE.md code quality improvements and add packaging

- Add #![forbid(unsafe_code)] to main.rs (issue #3)
- Replace raw ANSI escape codes with owo-colors crate (issue #2)
- Replace manual HOME path construction with dirs::home_dir() (issue #5)
- Ship umutray.service as a static file; service::install() substitutes
  the binary path at install time instead of generating the unit at runtime
- Add packaging/PKGBUILD following Arch Rust package guidelines
- Add CLAUDE.md tracking refactor tasks
- setup.rs: clean up downloaded temp files on abort/back, save launcher
  to config only after successful install, auto-start download when a
  preset has an installer_url
- util.rs: add pick_folder() using zenity/kdialog subprocesses (no rfd)
- config.rs: populate installer_url for all 6 built-in presets with
  official download URLs
- Document the Option<Option<Vec<String>>> gamescope pattern at main.rs:307

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/main.rs

@@ -1,3 +1,5 @@
+#![forbid(unsafe_code)]
+
 mod config;
 mod detect;
 mod diagnose;
@@ -11,6 +13,7 @@ mod util;
 
 use anyhow::Result;
 use clap::{Parser, Subcommand};
+use owo_colors::OwoColorize;
 use std::path::PathBuf;
 
 /// Tray-based Wine launcher manager for Linux via umu/Proton-GE.
@@ -105,7 +108,7 @@ enum Commands {
         action: ConfigAction,
     },
 
-    /// Manage the systemd --user service that autostarts the tray
+    /// Manage the XDG autostart entry that starts the tray on login
     Service {
         #[command(subcommand)]
         action: ServiceAction,
@@ -219,13 +222,13 @@ enum ConfigAction {
 
 #[derive(Subcommand)]
 enum ServiceAction {
-    /// Write the unit, daemon-reload, and enable+start the service (includes app menu entry)
+    /// Write ~/.config/autostart/umutray.desktop so the tray starts on login (includes app menu entry)
     Install,
-    /// Stop, disable, and remove the unit file (includes app menu entry)
+    /// Remove the autostart entry and app menu entry
     Uninstall,
-    /// Show `systemctl --user status` for the service
+    /// Show whether the XDG autostart entry is present
     Status,
-    /// Install only the app menu entry — no systemd service required
+    /// Install only the app menu entry
     InstallDesktop,
     /// Remove the app menu entry
     UninstallDesktop,
@@ -263,11 +266,7 @@ fn main() -> Result<()> {
             for l in &config.launchers {
                 let installed = l.full_exe_path().exists();
                 let running = launcher::is_running(l);
-                let marker = if installed {
-                    "\x1b[1;32m✓\x1b[0m"
-                } else {
-                    "·"
-                };
+                let marker = if installed { "✓".green().bold().to_string() } else { "·".to_string() };
                 let state = if running { " (running)" } else { "" };
                 println!("  {marker} {:12} {}{}", l.name, l.display, state);
             }
@@ -303,11 +302,7 @@ fn main() -> Result<()> {
                 println!("  {}:", l.display);
                 for g in &l.games {
                     let installed = g.full_exe_path(l).exists();
-                    let marker = if installed {
-                        "\x1b[1;32m✓\x1b[0m"
-                    } else {
-                        "·"
-                    };
+                    let marker = if installed { "✓".green().bold().to_string() } else { "·".to_string() };
                     let flags = format_game_flags(g);
                     println!("    {marker} {:14} {}{}", g.name, g.display, flags);
                 }
@@ -403,6 +398,10 @@ fn main() -> Result<()> {
                 gamescope,
                 no_gamescope,
             } => {
+                // gs_update is Option<Option<Vec<String>>> where:
+                //   None              = leave gamescope unchanged
+                //   Some(None)        = disable gamescope
+                //   Some(Some(args))  = enable gamescope with these CLI args
                 let gs_update = if no_gamescope {
                     Some(None)
                 } else {