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);
   });
 });