fix(engine): auto-complete delay + right-click shake on no legal move

Closes #80: add AUTO_COMPLETE_INITIAL_DELAY (0.75 s) before the first
auto-complete move fires. Previously cooldown was 0.0, causing the
sequence to hijack the board the same frame the condition was met.

Closes #81: fire MoveRejectedEvent in radial_open_on_right_click when
the right-clicked card has no legal destinations, so the shake
animation and invalid-move sound play consistently on desktop/web.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

solitaire_engine/src/auto_complete_plugin.rs

@@ -26,6 +26,12 @@ const AUTO_COMPLETE_CHIME_VOLUME: f64 = 0.5;
 /// Seconds between consecutive auto-complete moves.
 const STEP_INTERVAL: f32 = 0.12;
 
+/// Seconds to wait after detection before firing the first auto-complete move.
+///
+/// This pause gives the player a moment to register that the game is
+/// transitioning into auto-complete mode before cards start moving.
+const AUTO_COMPLETE_INITIAL_DELAY: f32 = 0.75;
+
 /// Tracks whether auto-complete is active and when the next move fires.
 #[derive(Resource, Default, Debug)]
 pub struct AutoCompleteState {
@@ -74,7 +80,7 @@ fn detect_auto_complete(
     }
     if game.0.is_auto_completable && !state.active {
         state.active = true;
-        state.cooldown = 0.0; // fire first move immediately
+        state.cooldown = AUTO_COMPLETE_INITIAL_DELAY;
     }
     // Intentionally no `else if !is_auto_completable` branch here.
     // Deactivating on every frame where `is_auto_completable` is false
@@ -210,6 +216,12 @@ mod tests {
         app.world_mut().resource_mut::<GameStateResource>().0 = nearly_won_state();
         app.world_mut().write_message(StateChangedEvent);
         app.update(); // detect runs, sets active
+
+        // Zero out the cooldown so drive fires on the next update regardless
+        // of the initial delay constant.
+        app.world_mut()
+            .resource_mut::<AutoCompleteState>()
+            .cooldown = 0.0;
         app.update(); // drive fires the move
 
         let events = app.world().resource::<Messages<MoveRequestEvent>>();

solitaire_engine/src/radial_menu.rs

@@ -52,7 +52,7 @@ use solitaire_core::game_state::GameState;
 use solitaire_core::pile::PileType;
 
 use crate::card_plugin::TABLEAU_FACEDOWN_FAN_FRAC;
-use crate::events::MoveRequestEvent;
+use crate::events::{MoveRejectedEvent, MoveRequestEvent};
 use crate::layout::{Layout, LayoutResource, TABLEAU_FAN_FRAC};
 use crate::pause_plugin::PausedResource;
 use crate::resources::{DragState, GameStateResource};
@@ -396,9 +396,10 @@ fn cursor_world(
 // ---------------------------------------------------------------------------
 
 /// On `MouseButton::Right` `just_pressed`, attempts to open the radial
-/// menu over the card the cursor is on. Skips when a left-mouse drag is
-/// in progress, when the game is paused, or when the clicked card has no
-/// legal destinations.
+/// menu over the card the cursor is on. When the cursor is on a face-up
+/// card but no legal destinations exist, fires `MoveRejectedEvent` so the
+/// shake animation and invalid-move sound play. Skips silently when no
+/// card is under the cursor, when a drag is in progress, or when paused.
 #[allow(clippy::too_many_arguments)]
 fn radial_open_on_right_click(
     buttons: Option<Res<ButtonInput<MouseButton>>>,
@@ -410,6 +411,7 @@ fn radial_open_on_right_click(
     layout: Option<Res<LayoutResource>>,
     game: Option<Res<GameStateResource>>,
     mut state: ResMut<RightClickRadialState>,
+    mut rejected: MessageWriter<MoveRejectedEvent>,
 ) {
     if paused.is_some_and(|p| p.0) {
         return;
@@ -438,6 +440,12 @@ fn radial_open_on_right_click(
     // cards and the highlight tint shows the same set the radial offers.
     let dests = legal_destinations_for_card(&card, &source_pile, &game.0);
     if dests.is_empty() {
+        // No legal destinations — shake the source pile as feedback.
+        rejected.write(MoveRejectedEvent {
+            from: source_pile.clone(),
+            to: source_pile,
+            count: 1,
+        });
         return;
     }
     let legal_destinations = build_radial_destinations(world, dests);
@@ -745,6 +753,7 @@ mod tests {
         let mut app = App::new();
         app.add_plugins(MinimalPlugins);
         app.add_message::<MoveRequestEvent>();
+        app.add_message::<MoveRejectedEvent>();
         app.init_resource::<DragState>();
         app.init_resource::<ButtonInput<MouseButton>>();
         app.init_resource::<ButtonInput<KeyCode>>();