feat(engine): Esc dismisses Home / accepts default on Restore prompt

Home and Restore-prompt previously ignored Esc, which after the last
fix meant Esc just did nothing on those screens. Now both honor the
"Esc closes the modal" convention every other modal already follows.

- Home: Esc behaves like the Cancel button — despawns the modal so
  the player keeps the underlying default deal.
- Restore: Esc maps to Continue rather than New Game; a reflexive
  dismiss press preserves the saved game, matching how the primary
  action already advertises the Enter accelerator.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

solitaire_engine/src/home_plugin.rs

@@ -333,10 +333,16 @@ fn handle_home_card_click(
 
 fn handle_home_cancel_button(
     mut commands: Commands,
+    keys: Option<Res<ButtonInput<KeyCode>>>,
     cancel_buttons: Query<&Interaction, (With<HomeCancelButton>, Changed<Interaction>)>,
     screens: Query<Entity, With<HomeScreen>>,
 ) {
-    if !cancel_buttons.iter().any(|i| *i == Interaction::Pressed) {
+    if screens.is_empty() {
+        return;
+    }
+    let click = cancel_buttons.iter().any(|i| *i == Interaction::Pressed);
+    let esc = keys.is_some_and(|k| k.just_pressed(KeyCode::Escape));
+    if !click && !esc {
         return;
     }
     for entity in &screens {