UI: fix last-move highlight, localize move history, clamp zoom overscroll

- Highlight tracks the last move overall (not the last word): a trailing
  pass/exchange now highlights nothing, so the board no longer lights up the
  opponent's old word after our own empty move.
- Make the highlight event-driven: refreshed only on a real game event
  (open/refresh, opponent move, our own committed move) and dismissed the moment
  composing starts, so recalling a just-placed tile never re-triggers it.
- Localize non-play move-history labels via new move.* catalog keys
  (pass/exchange/resign/timeout); the label printed the raw English action.
- Clamp the zoomed board's pan at its edge (overscroll-behavior: none), removing
  the native rubber-band past the content.

Tests: lastMoveCells unit coverage (trailing pass/exchange -> empty), i18n RU
label assertions, an e2e overscroll-contract check on the zoomed viewport.

ui/src/game/Board.svelte

@@ -228,6 +228,9 @@
   }
   .viewport.zoomed {
     overflow: auto;
+    /* Clamp the pan at the board edge: kill the native rubber-band/overscroll so the zoomed
+       board cannot be dragged past its content into empty space — it just stops at the edge. */
+    overscroll-behavior: none;
   }
   /* The query container is the (zoom-scaled) board, so cqw labels scale WITH the board
      — a magnifying-glass zoom. */

ui/src/game/Game.svelte

@@ -11,9 +11,9 @@
   import { app, handleError, showToast } from '../lib/app.svelte';
   import { connection } from '../lib/connection.svelte';
   import { GatewayError } from '../lib/client';
-  import { t } from '../lib/i18n/index.svelte';
+  import { t, type MessageKey } from '../lib/i18n/index.svelte';
   import type { Direction, EvalResult, MoveRecord, MoveResult, StateView, Tile } from '../lib/model';
-  import { replay } from '../lib/board';
+  import { lastMoveCells, replay } from '../lib/board';
   import { centre, premiumGrid } from '../lib/premiums';
   import { variantNameKey } from '../lib/variants';
   import { alphabetLetters, hasAlphabet } from '../lib/alphabet';
@@ -68,27 +68,48 @@
         .map((p) => [`${p.row},${p.col}`, { letter: p.letter, blank: p.blank }]),
     ),
   );
-  const lastPlay = $derived([...moves].reverse().find((m) => m.action === 'play') ?? null);
-  // Highlight the last word with a dark tile bg; while placing, only the pending tiles
-  // are highlighted. It flashes when the opponent just moved and it is now our turn.
-  const highlight = $derived(
-    placement.pending.length > 0 || !lastPlay || (!!view && view.game.status !== 'active')
-      ? new Set<string>()
-      : new Set(lastPlay.tiles.map((tt) => `${tt.row},${tt.col}`)),
-  );
-  const flash = $derived(
-    !!lastPlay &&
-      !!view &&
-      view.game.status === 'active' &&
-      lastPlay.player !== view.seat &&
-      view.game.toMove === view.seat,
-  );
+  // The recent-move highlight tracks the LAST move overall (not the last word): a play
+  // highlights its tiles, a trailing pass/exchange shows nothing — so the board never lights
+  // up the opponent's old word after our own pass. It is event-driven (refreshRecent), set
+  // only on a real game event (open/refresh, opponent move, our own committed move) and
+  // dismissed the moment we start composing, so recalling a just-placed tile never
+  // re-triggers it. recentFlash plays the one-off flash when the opponent just moved and it
+  // is now our turn.
+  let recent = $state<Set<string>>(new Set());
+  let recentFlash = $state(false);
+  function refreshRecent() {
+    const v = view;
+    if (!v || v.game.status !== 'active') {
+      recent = new Set();
+      recentFlash = false;
+      return;
+    }
+    recent = lastMoveCells(moves);
+    const last = moves.length ? moves[moves.length - 1] : null;
+    recentFlash = !!last && last.action === 'play' && last.player !== v.seat && v.game.toMove === v.seat;
+  }
+  $effect(() => {
+    // Composing dismisses the highlight until the next event refreshes it (so recalling the
+    // tiles we just placed leaves the board cleared, not re-lit).
+    if (placement.pending.length > 0) {
+      recent = new Set();
+      recentFlash = false;
+    }
+  });
   const slots = $derived(rackView(placement));
   const rackSlots = $derived(slots.map((s) => ({ ...s, id: rackIds[s.index] ?? s.index })));
   const isMyTurn = $derived(!!view && view.game.status === 'active' && view.game.toMove === view.seat);
   const gameOver = $derived(!!view && view.game.status !== 'active');
   const bagEmpty = $derived((view?.bagLen ?? 0) === 0);
 
+  // moveActionLabel localizes a non-play move's history label (pass/exchange/resign/timeout);
+  // an unknown action (forward-compat for the MoveAction string union) falls back to its raw
+  // wire string.
+  const MOVE_LABELS = new Set(['pass', 'exchange', 'resign', 'timeout']);
+  function moveActionLabel(action: string): string {
+    return MOVE_LABELS.has(action) ? t(`move.${action}` as MessageKey) : action;
+  }
+
   async function load() {
     try {
       // Ask for the alphabet table only on a per-variant cache miss (the first open of a
@@ -105,6 +126,7 @@
       dirOverride = undefined;
       await applyDraft(st);
       recompute();
+      refreshRecent();
     } catch (e) {
       handleError(e);
     }
@@ -149,6 +171,7 @@
       moves = cached.moves;
       placement = newPlacement(cached.view.rack);
       rackIds = cached.view.rack.map((_, i) => i);
+      refreshRecent();
     }
     void load();
     void loadFriends();
@@ -167,6 +190,7 @@
       moves = res.cache.moves;
       setCachedGame(id, view, moves);
       recompute();
+      refreshRecent();
     } else if (res.refetch) {
       void load();
     }
@@ -482,6 +506,7 @@
     selected = null;
     dirOverride = undefined;
     recompute();
+    refreshRecent();
   }
 
   async function commit() {
@@ -725,7 +750,7 @@
             {#each moves as m, i (i)}
               <li>
                 <span class="hp">{view.game.seats[m.player]?.displayName ?? m.player}</span>
-                <span class="ha">{m.action === 'play' ? m.words.join(', ') : m.action}</span>
+                <span class="ha">{m.action === 'play' ? m.words.join(', ') : moveActionLabel(m.action)}</span>
                 <span class="hs">{m.score} <span class="ht">({m.total})</span></span>
               </li>
             {/each}
@@ -748,8 +773,8 @@
           {board}
           {premium}
           pending={pendingMap}
-          {highlight}
-          {flash}
+          highlight={recent}
+          flash={recentFlash}
           centre={ctr}
           {zoomed}
           {variant}