refactor(engine): ambiguity gate covers the full cluster — batches 1-3, 585 pairs burned to zero

Port the July 7 gate-extender branch onto current master (the You-hub,
touch action bar, glass tab bar, Phase L, and hint-ghost work all landed
since) and finish batch 3. cluster_app now includes the mode, replay,
input, radial, tooltip, cursor, touch-selection, and safe-area plugins on
top of batches 1-2; the 585 ambiguous pairs the expansion exposed are
annotated down to zero and the gate stays assert_eq!(count, 0).

New ordering machinery:
- ReplayPlayback: playback driver chain on the pre-mutation spine
  (PointerInput < ReplayPlayback < overlay chain < GameMutation)
- ModeStart: mode-start handlers between the stats abandon-recorder and
  GameMutation; ChallengeCompletion < DailyCompletion < WeeklyGoalsEval
  pinned inside ProgressUpdate so `.after(ProgressUpdate)` readers see
  settled progress
- PointerInput: public set wrapping the input chain; AbandonRecord on the
  stats abandon-recorder; PendingHint around the async hint pipeline;
  HintGhostFx for the ghost chain (after the full visual spine)
- Clubs: MoveRequestWriters, WarningToastWriters join the existing
  request/toast writer clubs; UiTextFx grows the overlay/tooltip/safe-area
  chrome painters; SettingsAccess grows the lag-tolerant settings readers

Gate: cargo test --workspace green (993 engine tests), clippy
--all-targets -D warnings clean, rustfmt applied.

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

solitaire_engine/src/help_plugin.rs

@@ -54,12 +54,23 @@ impl Plugin for HelpPlugin {
             .add_message::<TouchInput>()
             .add_systems(
                 Update,
-                (
-                    toggle_help_screen,
-                    handle_help_close_button,
-                    scroll_help_panel,
-                    crate::ui_modal::touch_scroll_panel::<HelpScrollable>,
-                ),
+                (toggle_help_screen, handle_help_close_button)
+                    .chain()
+                    // FocusKeys consumes Esc after the modal handlers
+                    // (mirrors toggle_settings_screen, #143).
+                    .before(crate::ui_focus::FocusKeys),
+            )
+            .add_systems(
+                Update,
+                scroll_help_panel
+                    .in_set(crate::ui_modal::PanelScroll)
+                    .ambiguous_with(crate::ui_modal::PanelScroll),
+            )
+            .add_systems(
+                Update,
+                crate::ui_modal::touch_scroll_panel::<HelpScrollable>
+                    .in_set(crate::ui_modal::PanelScroll)
+                    .ambiguous_with(crate::ui_modal::PanelScroll),
             );
     }
 }