feat(engine): Phase F touch action bar — thumb-reach Undo/Draw/Hint + hold-to-repeat undo

Touch layout (USE_TOUCH_UI_LAYOUT) restructures the bottom action bar
to five buttons: an enlarged Undo / Draw / Hint trio (96x64px targets,
1.35x labels) between compact Menu and Pause. Draw is new — it fires
the same DrawRequestEvent as tapping the stock, so the most frequent
action no longer needs a reach to the top of a tall folded screen.
Help, Modes, and New Game leave the touch bar (they live in Menu ->
System, the Home grid, and Home's hero respectively). Desktop keeps
the seven-button bar unchanged (decision 5: touch-only).

Holding Undo now steps back repeatedly after a 0.45s delay (5.5/s),
each step through the normal request path so the scoring penalty
applies. New self-ambiguous DrawRequestWriters set keeps the ambiguity
gate at zero with the fourth DrawRequestEvent writer.

6 new hud_plugin tests; workspace suite + clippy green.

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

solitaire_engine/src/hud_plugin/mod.rs

@@ -28,7 +28,7 @@ struct AvatarResource(Option<bevy::prelude::Handle<bevy::prelude::Image>>);
 use crate::challenge_plugin::CHALLENGE_UNLOCK_LEVEL;
 use crate::daily_challenge_plugin::DailyChallengeResource;
 use crate::events::{
-    HelpRequestEvent, InfoToastEvent, NewGameRequestEvent, PauseRequestEvent,
+    DrawRequestEvent, HelpRequestEvent, InfoToastEvent, NewGameRequestEvent, PauseRequestEvent,
     StartChallengeRequestEvent, StartDailyChallengeRequestEvent, StartTimeAttackRequestEvent,
     StartZenRequestEvent, ToggleAchievementsRequestEvent, ToggleHomeRequestEvent,
     ToggleLeaderboardRequestEvent, ToggleProfileRequestEvent, ToggleSettingsRequestEvent,
@@ -313,6 +313,18 @@ pub struct UndoButton;
 #[derive(Component, Debug)]
 pub struct PauseButton;
 
+/// Accumulated hold time on the Undo button, driving hold-to-repeat undo
+/// (Phase F). `handle_undo_button` owns the instant first undo on press;
+/// `repeat_undo_on_hold` starts firing additional [`UndoRequestEvent`]s
+/// once the hold passes `UNDO_HOLD_INITIAL_DELAY_SECS` and then every
+/// `UNDO_HOLD_REPEAT_INTERVAL_SECS`. Each repeated undo goes through the
+/// normal request path, so the existing scoring penalty applies per step.
+#[derive(Resource, Debug, Default)]
+pub struct UndoHoldState {
+    /// Seconds the Undo button has been continuously held.
+    held_secs: f32,
+}
+
 /// Marker on the "Help" action button. Click fires [`HelpRequestEvent`],
 /// mirroring the `F1` keyboard accelerator.
 #[derive(Component, Debug)]
@@ -323,31 +335,27 @@ pub struct HelpButton;
 #[derive(Component, Debug)]
 pub struct HintButton;
 
+/// Marker on the touch action bar's "Draw" button (Phase F). Click fires
+/// [`DrawRequestEvent`] — same queue as tapping the stock pile — so the
+/// draw action is within thumb reach without stretching to the top of a
+/// tall folded screen. Touch layout only; desktop draws via stock
+/// click / `D` / `Space`.
+#[derive(Component, Debug)]
+pub struct DrawButton;
+
 /// Android HUD label for the Hint button — shared with the help screen's
 /// controls reference so both always agree.
 #[cfg(target_os = "android")]
 pub(crate) const ANDROID_HINT_LABEL: &str = "Hint";
 
+/// Hint label used by the touch action bar. Aliases [`ANDROID_HINT_LABEL`]
+/// on Android so the bar and the help screen's controls reference can
+/// never drift; the non-Android value only exists so the touch spawn
+/// path stays host-compilable for tests.
 #[cfg(target_os = "android")]
-const ACTION_BAR_LABELS: [&str; 7] = [
-    "Menu",
-    "Undo",
-    "Pause",
-    "Help",
-    ANDROID_HINT_LABEL,
-    "Mode",
-    "New",
-];
+const TOUCH_HINT_LABEL: &str = ANDROID_HINT_LABEL;
 #[cfg(not(target_os = "android"))]
-const ACTION_BAR_LABELS: [&str; 7] = [
-    "Menu \u{2193}",
-    "Undo",
-    "Pause",
-    "Help",
-    "Hint",
-    "Modes \u{2193}",
-    "New Game",
-];
+const TOUCH_HINT_LABEL: &str = "Hint";
 #[cfg(target_os = "android")]
 const ACTION_BAR_COLUMN_GAP: Val = Val::Px(4.0);
 #[cfg(not(target_os = "android"))]
@@ -455,6 +463,7 @@ impl Plugin for HudPlugin {
         // idempotent.
         app.add_message::<NewGameRequestEvent>()
             .add_message::<UndoRequestEvent>()
+            .add_message::<DrawRequestEvent>()
             .add_message::<PauseRequestEvent>()
             .add_message::<HelpRequestEvent>()
             .add_message::<StartZenRequestEvent>()
@@ -471,6 +480,7 @@ impl Plugin for HudPlugin {
             .init_resource::<PreviousScore>()
             .init_resource::<HudActionFade>()
             .init_resource::<HudVisibility>()
+            .init_resource::<UndoHoldState>()
             // Escape-close handlers for popovers read this; init defensively
             // so HudPlugin works under MinimalPlugins in tests.
             .init_resource::<ButtonInput<KeyCode>>()
@@ -560,6 +570,14 @@ impl Plugin for HudPlugin {
                         .in_set(crate::game_plugin::UndoRequestWriters)
                         .ambiguous_with(crate::game_plugin::UndoRequestWriters)
                         .before(GameMutation),
+                    repeat_undo_on_hold
+                        .in_set(crate::game_plugin::UndoRequestWriters)
+                        .ambiguous_with(crate::game_plugin::UndoRequestWriters)
+                        .before(GameMutation),
+                    handle_draw_button
+                        .in_set(crate::game_plugin::DrawRequestWriters)
+                        .ambiguous_with(crate::game_plugin::DrawRequestWriters)
+                        .before(GameMutation),
                     handle_pause_button,
                     handle_help_button,
                     handle_hint_button