fix(web client): show jans arrows

clients/web/src/game/components/game_screen.rs

@@ -176,7 +176,7 @@ pub fn GameScreen(state: GameUiState) -> impl IntoView {
 
     let last_moves = state.last_moves;
 
-    // §6e — fields where a battue (hit) was scored; ripple animation shown there.
+    // fields where a battue (hit) was scored; ripple animation shown there.
     let hit_fields: Vec<u8> = {
         let is_hit_jan = |jan: &Jan| {
             matches!(
@@ -337,7 +337,7 @@ pub fn GameScreen(state: GameUiState) -> impl IntoView {
                 hit_fields=hit_fields
             />
 
-            // ── Status, hints, and actions — cream strip below board (§10b/c) ─
+            // ── Status, hints, and actions — cream strip below board ─
             <div class="game-bottom-strip">
                 <div class="game-status">
                     {move || {

clients/web/src/game/components/scoring.rs

@@ -80,8 +80,7 @@ pub fn ScoringPanel(
         "scoring-panel"
     };
 
-    // minimized: starts false (expanded), becomes true after 3.4 s unless
-    // the Hold/Go choice still needs the player's attention.
+    // minimized: starts false (expanded)
     let minimized = RwSignal::new(false);
 
     // Collect all moves from all jans for automatic arrow display.
@@ -97,6 +96,43 @@ pub fn ScoringPanel(
     let hovered_ctx = use_context::<RwSignal<Vec<(CheckerMove, CheckerMove)>>>();
     let jan_rows: Vec<_> = event.jans.into_iter().map(scoring_jan_row).collect();
 
+    // On mount: show all this event's moves as board arrows immediately,
+    // then after 3.4 s slide to peek and clear the arrows.
+    //
+    // Two important constraints:
+    // 1. The initial hm.set() must be deferred (spawn_local, not sync in body)
+    //    to avoid writing a reactive signal mid-render while Board reads it —
+    //    that triggers Leptos's cycle guard → `unreachable` WASM panic.
+    // 2. The cancellation flag must be Rc<Cell<bool>>, NOT RwSignal<bool>.
+    //    RwSignal is a NodeId into Leptos's arena; the arena slot is freed
+    //    when ScoringPanel's owner drops (on every GameScreen remount). If the
+    //    3.4 s future outlives the component and calls is_alive.get_untracked()
+    //    on a freed slot, that also panics with `unreachable`. Rc<Cell<bool>>
+    //    is reference-counted outside the arena and stays valid for as long as
+    //    the future holds onto it.
+    #[cfg(target_arch = "wasm32")]
+    if let Some(hm) = hovered_ctx {
+        let is_alive = Arc::new(AtomicBool::new(true));
+        let is_alive_cleanup = is_alive.clone();
+        // on_cleanup requires Send + Sync; Arc<AtomicBool> satisfies both.
+        on_cleanup(move || is_alive_cleanup.store(false, Ordering::Relaxed));
+
+        spawn_local(async move {
+            // Show arrows (runs in the next microtask, after render settles).
+            hm.set(all_moves);
+
+            TimeoutFuture::new(3_400).await;
+            // Guard: component may have been destroyed while we were waiting.
+            // is_alive was set to false by on_cleanup, which runs before Leptos
+            // frees the signal arena slots — so peeked is still valid iff this
+            // returns true.
+            if !is_alive.load(Ordering::Relaxed) {
+                return;
+            }
+            hm.set(vec![]);
+        });
+    }
+
     view! {
         <div
             class="scoring-panel-wrapper"