fix(engine): swallow game-mutating hotkeys during pointer drags

U (undo), N (new game), Z (zen), D/Space (draw) and G (forfeit) were
not gated on an active drag, so pressing one mid-drag fired a
StateChangedEvent whose card re-sync inserted a `CardAnim` on the
dragged cards — fighting `follow_drag`'s per-frame Transform writes
(jittering XY, animated Z) and leaving `DragState` origin indices
stale against the mutated state.

`handle_keyboard_core` and `handle_keyboard_forfeit` now reuse the
mutual-exclusion guard `handle_selection_keys` already documents: skip
while `DragState` is non-idle, unless it is the keyboard-lift sentinel
(`KEYBOARD_DRAG_TOUCH_ID`), whose lift is already dropped cleanly by
`clear_selection_on_state_change`.

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

solitaire_engine/src/input_plugin/mod.rs

@@ -215,6 +215,7 @@ fn handle_keyboard_core(
     keys: Res<ButtonInput<KeyCode>>,
     paused: Option<Res<PausedResource>>,
     progress: Option<Res<ProgressResource>>,
+    drag: Res<DragState>,
     mut ev: CoreKeyboardMessages<'_>,
     mut time_attack: Option<ResMut<TimeAttackResource>>,
     selection: Option<Res<SelectionState>>,
@@ -227,6 +228,19 @@ fn handle_keyboard_core(
         return;
     }
 
+    // Mutual exclusion with pointer drags — mirrors `handle_selection_keys`.
+    // Undo / draw / new-game during an active mouse or touch drag would fire
+    // a StateChangedEvent whose card re-sync inserts a `CardAnim` on the
+    // dragged cards, fighting `follow_drag`'s per-frame Transform writes and
+    // leaving `DragState` origin indices stale against the mutated state.
+    // The keyboard-drag sentinel may proceed: `clear_selection_on_state_change`
+    // already drops that lift cleanly when the state moves.
+    if !drag.is_idle()
+        && drag.active_touch_id != Some(crate::selection_plugin::KEYBOARD_DRAG_TOUCH_ID)
+    {
+        return;
+    }
+
     // During replay playback (Playing or Completed) all game-input shortcuts
     // are suppressed. The replay overlay owns Space (pause/resume) and the
     // arrow keys (step). Letting game input through would mutate
@@ -473,11 +487,19 @@ pub fn emit_hint_visuals(
 fn handle_keyboard_forfeit(
     keys: Res<ButtonInput<KeyCode>>,
     paused: Option<Res<PausedResource>>,
+    drag: Res<DragState>,
     mut requests: MessageWriter<ForfeitRequestEvent>,
 ) {
     if paused.is_some_and(|p| p.0) {
         return;
     }
+    // Same pointer-drag exclusion as `handle_keyboard_core` — forfeiting
+    // mid-drag would mutate the game state under the dragged cards.
+    if !drag.is_idle()
+        && drag.active_touch_id != Some(crate::selection_plugin::KEYBOARD_DRAG_TOUCH_ID)
+    {
+        return;
+    }
     if !keys.just_pressed(KeyCode::KeyG) {
         return;
     }