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/lib/board.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest';
-import { lastPlayTiles, replay } from './board';
+import { lastMoveCells, replay } from './board';
 import type { MoveRecord } from './model';
 
 function play(tiles: { row: number; col: number; letter: string; blank: boolean }[]): MoveRecord {
@@ -17,18 +17,11 @@ function play(tiles: { row: number; col: number; letter: string; blank: boolean
   };
 }
 
-const pass: MoveRecord = {
-  player: 1,
-  action: 'pass',
-  dir: '',
-  mainRow: 0,
-  mainCol: 0,
-  tiles: [],
-  words: [],
-  count: 0,
-  score: 0,
-  total: 0,
-};
+function simple(action: 'pass' | 'exchange'): MoveRecord {
+  return { player: 1, action, dir: '', mainRow: 0, mainCol: 0, tiles: [], words: [], count: 0, score: 0, total: 0 };
+}
+
+const pass = simple('pass');
 
 describe('board replay', () => {
   it('places play tiles and ignores non-play moves', () => {
@@ -48,10 +41,31 @@ describe('board replay', () => {
     expect(b.length).toBe(15);
     expect(b[0].length).toBe(15);
   });
+});
 
-  it('lastPlayTiles returns the most recent play, skipping passes', () => {
+describe('lastMoveCells', () => {
+  it('returns the last move cells when the last move is a play', () => {
+    const moves = [
+      pass,
+      play([
+        { row: 7, col: 7, letter: 'A', blank: false },
+        { row: 7, col: 8, letter: 'B', blank: false },
+      ]),
+    ];
+    expect(lastMoveCells(moves)).toEqual(new Set(['7,7', '7,8']));
+  });
+
+  it('highlights nothing when the last move is a pass after a play', () => {
     const moves = [play([{ row: 7, col: 7, letter: 'A', blank: false }]), pass];
-    expect(lastPlayTiles(moves)).toHaveLength(1);
-    expect(lastPlayTiles([pass])).toHaveLength(0);
+    expect(lastMoveCells(moves).size).toBe(0);
+  });
+
+  it('highlights nothing when the last move is an exchange', () => {
+    const moves = [play([{ row: 7, col: 7, letter: 'A', blank: false }]), simple('exchange')];
+    expect(lastMoveCells(moves).size).toBe(0);
+  });
+
+  it('highlights nothing for an empty journal', () => {
+    expect(lastMoveCells([]).size).toBe(0);
   });
 });

ui/src/lib/board.ts

@@ -3,7 +3,7 @@
 // the dictionary-independent history invariant (ARCHITECTURE §9.1): apply each play's
 // placed tiles onto an empty grid.
 
-import type { MoveRecord, Tile } from './model';
+import type { MoveRecord } from './model';
 import { BOARD_SIZE } from './premiums';
 
 export interface BoardCell {
@@ -36,10 +36,11 @@ export function replay(moves: MoveRecord[]): Board {
   return b;
 }
 
-/** lastPlayTiles returns the tiles of the most recent play (for highlighting). */
-export function lastPlayTiles(moves: MoveRecord[]): Tile[] {
-  for (let i = moves.length - 1; i >= 0; i--) {
-    if (moves[i].action === 'play') return moves[i].tiles;
-  }
-  return [];
+/** lastMoveCells returns the cells of the last move's tiles (as "row,col" keys), but only
+ * when that move placed tiles (a play). A trailing pass/exchange/resign/timeout highlights
+ * nothing — the recent-move highlight tracks the last move overall, not the last word. */
+export function lastMoveCells(moves: MoveRecord[]): Set<string> {
+  const last = moves.length ? moves[moves.length - 1] : null;
+  if (!last || last.action !== 'play') return new Set();
+  return new Set(last.tiles.map((t) => `${t.row},${t.col}`));
 }

ui/src/lib/i18n.test.ts

@@ -13,6 +13,12 @@ describe('i18n catalog', () => {
     expect(translate('ru', 'game.bag', { n: 7 })).toBe('7 в мешке');
   });
 
+  it('localizes move-history action labels', () => {
+    expect(translate('ru', 'move.exchange')).toBe('Обмен');
+    expect(translate('ru', 'move.pass')).toBe('Пас');
+    expect(translate('en', 'move.exchange')).toBe('Exchange');
+  });
+
   it('maps error codes to keys with a generic fallback', () => {
     expect(errorKey('not_your_turn')).toBe('error.not_your_turn');
     expect(errorKey('totally_unknown')).toBe('error.generic');

ui/src/lib/i18n/en.ts

@@ -88,6 +88,11 @@ export const en = {
   'game.noHintOptions': 'No options with your letters.',
   'game.scores': 'Scores: {n}',
 
+  'move.pass': 'Pass',
+  'move.exchange': 'Exchange',
+  'move.resign': 'Resigned',
+  'move.timeout': 'Timed out',
+
   'result.victory': 'Victory',
   'result.defeat': 'Defeat',
   'result.draw': 'Draw',

ui/src/lib/i18n/ru.ts

@@ -89,6 +89,11 @@ export const ru: Record<MessageKey, string> = {
   'game.noHintOptions': 'Нет вариантов с вашим набором.',
   'game.scores': 'Очков: {n}',
 
+  'move.pass': 'Пас',
+  'move.exchange': 'Обмен',
+  'move.resign': 'Сдача',
+  'move.timeout': 'Тайм-аут',
+
   'result.victory': 'Победа',
   'result.defeat': 'Поражение',
   'result.draw': 'Ничья',