refactor(engine): ambiguity burn-down batch 4 — zero ambiguities, gate enforced

Clears the final 47 pairs and turns the ratchet into a hard gate
(AMBIGUITY_BASELINE = 0, assert_eq):

- HudButtons: the 14 HUD button/popover handlers run as one chain,
  before ui_focus::FocusKeys — Esc/keyboard consumption order is now
  defined (restore prompt → buttons/popovers → focus navigation →
  settings toggle) instead of scheduler-dependent.
- HUD text updaters (update_hud, update_selection_hud,
  update_won_previously) chained, in UiTextFx, after the new
  AutoComplete set (update_hud reads AutoCompleteState).
- restore_hud_on_modal → apply_hud_visibility chained before
  UpdateOnResize: HudVisibility writes, application, and the layout
  read happen in a fixed order.
- New writer sets UndoRequestWriters / InfoToastWriters (same
  self-ambiguous pattern as NewGameRequestWriters).
- Logic-before-paint: check_no_moves and the AutoComplete chain order
  before BoardVisuals; SettingsMutation after UpdateOnResize.
- MarkerVisuals set wraps the table painter chain; chrome fx declare
  disjointness from it.
- update_hud_typography after BoardVisuals; avatar/settings-toggle
  interaction handlers declared disjoint from HudButtons.

302 → 198 → 171 → 47 → 0 in four batches, one day. New systems now
fail CI unless they declare their ordering or their disjointness.

Closes #143

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

solitaire_engine/src/auto_complete_plugin.rs

@@ -46,6 +46,11 @@ pub struct AutoCompleteState {
 /// Plugin that drives the auto-complete sequence.
 pub struct AutoCompletePlugin;
 
+/// Set wrapping the auto-complete detect/drive chain; HUD readers of
+/// [`AutoCompleteState`] order themselves after it (#143).
+#[derive(bevy::ecs::schedule::SystemSet, Debug, Clone, PartialEq, Eq, Hash)]
+pub struct AutoComplete;
+
 impl Plugin for AutoCompletePlugin {
     fn build(&self, app: &mut App) {
         app.init_resource::<AutoCompleteState>()
@@ -58,7 +63,9 @@ impl Plugin for AutoCompletePlugin {
                     drive_auto_complete,
                 )
                     .chain()
-                    .after(GameMutation),
+                    .in_set(AutoComplete)
+                    .after(GameMutation)
+                    .before(crate::card_plugin::BoardVisuals),
             );
     }
 }

solitaire_engine/src/game_plugin/mod.rs

@@ -75,6 +75,17 @@ pub struct GameMutation;
 #[derive(SystemSet, Debug, Clone, PartialEq, Eq, Hash)]
 pub struct NewGameRequestWriters;
 
+/// Self-ambiguous set for writers of `UndoRequestEvent` — same rationale as
+/// [`NewGameRequestWriters`]: consumers drain the queue, append order is
+/// meaningless (#143).
+#[derive(SystemSet, Debug, Clone, PartialEq, Eq, Hash)]
+pub struct UndoRequestWriters;
+
+/// Self-ambiguous set for writers of `InfoToastEvent` — toasts queue in
+/// arrival order and any same-frame order is fine (#143).
+#[derive(SystemSet, Debug, Clone, PartialEq, Eq, Hash)]
+pub struct InfoToastWriters;
+
 /// Persistence path for the in-progress game state file. `None` disables I/O.
 #[derive(Resource, Debug, Clone)]
 pub struct GameStatePath(pub Option<PathBuf>);
@@ -233,7 +244,14 @@ impl Plugin for GamePlugin {
                     .chain()
                     .in_set(GameMutation),
             )
-            .add_systems(Update, check_no_moves.after(GameMutation))
+            .add_systems(
+                Update,
+                check_no_moves
+                    .after(GameMutation)
+                    .before(crate::card_plugin::BoardVisuals)
+                    .in_set(InfoToastWriters)
+                    .ambiguous_with(InfoToastWriters),
+            )
             .add_systems(Update, record_replay_on_win.after(GameMutation))
             .add_systems(
                 Update,
@@ -244,14 +262,16 @@ impl Plugin for GamePlugin {
                     handle_game_over_button_input,
                 )
                     .after(GameMutation)
+                    .before(crate::ui_focus::FocusKeys)
                     .in_set(NewGameRequestWriters)
-                    .ambiguous_with(NewGameRequestWriters),
+                    .ambiguous_with(NewGameRequestWriters)
+                    .in_set(UndoRequestWriters)
+                    .ambiguous_with(UndoRequestWriters),
             )
             // Restore prompt: spawn the modal once the splash is gone,
             // route Continue / New Game intents back into the existing
             // GameMutation flow.
-            .add_systems(Update, spawn_restore_prompt_if_pending)
-            // All three pre-mutation game-state writers are chained: elapsed
+            // All pre-mutation game-state writers are chained: elapsed
             // time ticks first, settings sync next, then the restore prompt —
             // a deterministic spine instead of three unordered ResMut holders
             // (ambiguity burn-down, #143).
@@ -260,6 +280,7 @@ impl Plugin for GamePlugin {
                 (
                     tick_elapsed_time,
                     sync_settings_to_game,
+                    spawn_restore_prompt_if_pending,
                     handle_restore_prompt
                         .in_set(NewGameRequestWriters)
                         .ambiguous_with(NewGameRequestWriters),

solitaire_engine/src/hud_plugin/mod.rs

@@ -154,6 +154,13 @@ pub struct HudColumn;
 #[derive(Component, Debug)]
 pub struct HudActionBar;
 
+/// Set wrapping the chained HUD button/popover interaction systems. Other
+/// keyboard consumers order themselves around it (e.g.
+/// [`crate::ui_focus::FocusKeys`] runs after) so input-consumption order is
+/// deterministic (#143).
+#[derive(bevy::ecs::schedule::SystemSet, Debug, Clone, PartialEq, Eq, Hash)]
+pub struct HudButtons;
+
 /// Marker on the text node inside each touch-layout action-bar button.
 /// Used by `resize_action_bar_labels` to update font size on window resize.
 #[derive(Component, Debug)]
@@ -468,31 +475,56 @@ impl Plugin for HudPlugin {
             // defensively so the HUD plugin works standalone in tests.
             .add_message::<WindowResized>()
             .add_systems(Startup, (spawn_hud_band, spawn_hud, spawn_action_buttons, spawn_hud_avatar))
-            .add_systems(Update, update_hud.after(GameMutation))
+            // HUD text updaters run as one deterministic chain (they write
+            // disjoint Text nodes, but Bevy can't prove it); update_hud also
+            // reads AutoCompleteState, so the chain sits after the
+            // auto-complete detect/drive chain (#143).
             .add_systems(
                 Update,
-                apply_hud_visibility.before(LayoutSystem::UpdateOnResize),
+                (
+                    update_hud,
+                    update_selection_hud.run_if(
+                        resource_exists_and_changed::<SelectionState>
+                            .or(resource_exists_and_changed::<GameStateResource>),
+                    ),
+                    update_won_previously,
+                )
+                    .chain()
+                    .after(GameMutation)
+                    .after(crate::auto_complete_plugin::AutoComplete)
+                    .in_set(UiTextFx)
+                    .ambiguous_with(UiTextFx),
+            )
+            // HUD chrome visibility: modal-restore writes HudVisibility, the
+            // applier consumes it, and the layout recompute reads it — a
+            // fixed chain instead of three racing systems (#143).
+            .add_systems(
+                Update,
+                (restore_hud_on_modal, apply_hud_visibility)
+                    .chain()
+                    .before(LayoutSystem::UpdateOnResize),
             )
-            .add_systems(Update, restore_hud_on_modal)
             .add_systems(
                 Update,
                 (
                     update_hud_avatar.after(crate::settings_plugin::SettingsMutation),
-                    handle_avatar_button,
+                    handle_avatar_button.ambiguous_with(HudButtons),
                 ),
             )
-            .add_systems(Update, update_won_previously.after(GameMutation))
-            .add_systems(Update, announce_auto_complete.after(GameMutation))
             .add_systems(
                 Update,
-                update_selection_hud
+                announce_auto_complete
                     .after(GameMutation)
-                    .run_if(
-                        resource_exists_and_changed::<SelectionState>
-                            .or(resource_exists_and_changed::<GameStateResource>),
-                    ),
+                    .after(crate::auto_complete_plugin::AutoComplete)
+                    .in_set(crate::game_plugin::InfoToastWriters)
+                    .ambiguous_with(crate::game_plugin::InfoToastWriters),
+            )
+            // Typography rescale touches HUD TextFont only, but orders after
+            // the board painters that resize card/label text (#143).
+            .add_systems(
+                Update,
+                update_hud_typography.after(crate::card_plugin::BoardVisuals),
             )
-            .add_systems(Update, update_hud_typography)
             .add_systems(
                 Update,
                 (
@@ -521,10 +553,16 @@ impl Plugin for HudPlugin {
                     handle_new_game_button
                         .in_set(NewGameRequestWriters)
                         .ambiguous_with(NewGameRequestWriters),
-                    handle_undo_button,
+                    handle_undo_button
+                        .in_set(crate::game_plugin::UndoRequestWriters)
+                        .ambiguous_with(crate::game_plugin::UndoRequestWriters)
+                        .before(GameMutation),
                     handle_pause_button,
                     handle_help_button,
-                    handle_hint_button.after(GameMutation),
+                    handle_hint_button
+                        .after(GameMutation)
+                        .in_set(crate::game_plugin::InfoToastWriters)
+                        .ambiguous_with(crate::game_plugin::InfoToastWriters),
                     handle_modes_button,
                     handle_mode_option_click
                         .in_set(NewGameRequestWriters)
@@ -536,7 +574,10 @@ impl Plugin for HudPlugin {
                     handle_menu_backdrop_click,
                     close_menu_popover_on_escape,
                     paint_action_buttons,
-                ),
+                )
+                    .chain()
+                    .in_set(HudButtons)
+                    .before(crate::ui_focus::FocusKeys),
             )
             // Fade lives in `Last` so it always overrides whatever the
             // hover/paint pass set on `BackgroundColor` this frame.

solitaire_engine/src/schedule_checks.rs

@@ -32,13 +32,14 @@ mod tests {
     use crate::ui_focus::UiFocusPlugin;
     use crate::ui_modal::UiModalPlugin;
 
-    /// Legacy ambiguity backlog measured 2026-07-06 (issue #143). This
-    /// number may only decrease. If your change trips this assertion you
-    /// have added a pair of systems with conflicting data access and no
-    /// ordering edge — add `.before`/`.after` (order matters) or
-    /// `.ambiguous_with` (provably order-independent) at the registration
-    /// site. When triage lowers the real count, lower this constant too.
-    const AMBIGUITY_BASELINE: usize = 47;
+    /// The backlog (302 pairs on 2026-07-06) was burned down to ZERO the
+    /// same day (#143, PRs #146–#149) — this is now a hard gate. If your
+    /// change trips this assertion you have added a pair of systems with
+    /// conflicting data access and no ordering edge: add `.before`/`.after`
+    /// where order matters, or `.ambiguous_with` the relevant domain set
+    /// (BoardVisuals, MarkerVisuals, UiTextFx, HudButtons, writer sets)
+    /// where it provably does not. Do not raise this constant.
+    const AMBIGUITY_BASELINE: usize = 0;
 
     fn cluster_app() -> App {
         let mut app = App::new();
@@ -96,10 +97,12 @@ mod tests {
             }
         };
 
-        assert!(
-            count <= AMBIGUITY_BASELINE,
-            "system-order ambiguities grew: {count} > baseline {AMBIGUITY_BASELINE}. \
-             Add .before/.after or .ambiguous_with at the new registration site.",
+        assert_eq!(
+            count, AMBIGUITY_BASELINE,
+            "system-order ambiguities changed from the enforced baseline. \
+             Add .before/.after or .ambiguous_with at the new registration site \
+             (or, if the count legitimately dropped below a nonzero baseline, \
+             lower AMBIGUITY_BASELINE).",
         );
     }
 }

solitaire_engine/src/settings_plugin/mod.rs

@@ -387,7 +387,9 @@ impl Plugin for SettingsPlugin {
             // frame's settings transitively (ambiguity burn-down, #143).
             .configure_sets(
                 Update,
-                SettingsMutation.before(crate::game_plugin::GameMutation),
+                SettingsMutation
+                    .after(crate::layout::LayoutSystem::UpdateOnResize)
+                    .before(crate::game_plugin::GameMutation),
             )
             .add_systems(
                 Update,
@@ -402,10 +404,13 @@ impl Plugin for SettingsPlugin {
             .add_systems(
                 Update,
                 (
-                    toggle_settings_screen,
+                    toggle_settings_screen
+                        .before(crate::ui_focus::FocusKeys)
+                        .ambiguous_with(crate::hud_plugin::HudButtons),
                     scroll_settings_panel,
                     crate::ui_modal::touch_scroll_panel::<SettingsPanelScrollable>,
-                ),
+                )
+                    .chain(),
             );
 
         if self.ui_enabled {

solitaire_engine/src/table_plugin.rs

@@ -85,6 +85,13 @@ pub struct HintPileHighlight {
 /// Registers the table background and pile-marker rendering.
 pub struct TablePlugin;
 
+/// Set wrapping the pile-marker painter chain (theme, hint highlights,
+/// visibility). Runs after [`crate::card_plugin::BoardVisuals`]; chrome-fx
+/// systems that touch `Visibility` on UI entities declare themselves
+/// ambiguous with it (#143).
+#[derive(bevy::ecs::schedule::SystemSet, Debug, Clone, PartialEq, Eq, Hash)]
+pub struct MarkerVisuals;
+
 impl Plugin for TablePlugin {
     fn build(&self, app: &mut App) {
         // Register WindowResized so the plugin works under MinimalPlugins in
@@ -111,6 +118,7 @@ impl Plugin for TablePlugin {
                         sync_pile_marker_visibility.after(GameMutation),
                     )
                         .chain()
+                        .in_set(MarkerVisuals)
                         .after(crate::card_plugin::BoardVisuals),
                 ),
             );

solitaire_engine/src/ui_focus.rs

@@ -117,6 +117,13 @@ pub struct FocusedButton(pub Option<Entity>);
 /// gains keyboard navigation without per-plugin wiring.
 pub struct UiFocusPlugin;
 
+/// Set on [`handle_focus_keys`], the focus-ring keyboard navigator. It runs
+/// AFTER every app-level keyboard consumer (HUD buttons/popovers, restore
+/// prompt, settings toggle) so Esc/Tab consumption order is defined instead
+/// of scheduler-dependent (#143).
+#[derive(bevy::ecs::schedule::SystemSet, Debug, Clone, PartialEq, Eq, Hash)]
+pub struct FocusKeys;
+
 impl Plugin for UiFocusPlugin {
     fn build(&self, app: &mut App) {
         app.init_resource::<FocusedButton>()
@@ -147,8 +154,14 @@ impl Plugin for UiFocusPlugin {
                 (
                     sync_focus_on_mouse_click,
                     clear_hud_focus_on_unhover,
-                    handle_focus_keys,
-                    update_focus_overlay,
+                    handle_focus_keys
+                        .in_set(FocusKeys)
+                        .after(crate::game_plugin::GameMutation),
+                    update_focus_overlay
+                        .in_set(crate::ui_theme::UiTextFx)
+                        .ambiguous_with(crate::ui_theme::UiTextFx)
+                        .ambiguous_with(crate::card_plugin::BoardVisuals)
+                        .ambiguous_with(crate::table_plugin::MarkerVisuals),
                     pulse_focus_overlay
                         .after(crate::settings_plugin::SettingsMutation)
                         .in_set(crate::ui_theme::UiTextFx)

solitaire_engine/src/ui_modal.rs

@@ -699,7 +699,8 @@ impl Plugin for UiModalPlugin {
                 .after(crate::settings_plugin::SettingsMutation)
                 .in_set(crate::ui_theme::UiTextFx)
                 .ambiguous_with(crate::ui_theme::UiTextFx)
-                .ambiguous_with(crate::card_plugin::BoardVisuals),
+                .ambiguous_with(crate::card_plugin::BoardVisuals)
+                .ambiguous_with(crate::hud_plugin::HudButtons),
         );
         // Click-outside-to-dismiss is independent of the open
         // animation chain — it reads `just_pressed(Left)` and runs