fix(ui): advance turn glow/interactivity to the player to move

`active` was `$derived(gameStore.activeBoards)`, and that getter read the
non-`$state` `#game`. The $derived captured no reactive dependency, so the
glowing/interactive boards froze on North's NW+NE after move 1: the next
player couldn't act, clicks on their boards did nothing, and selections fired
on unexpected boards — the reported "turns", "what piece is selected", and
"mirrored movements" symptoms were all this one stale-derived bug.

Fix: derive `active` from the reactive `view.currentPlayer`; remove the
footgun `activeBoards` getter so nothing re-reads `#game` reactively.

Add scripts/smoke.py: Playwright end-to-end test driving the real app through
a full N->S->E->W round (engine vitest can't see Svelte reactivity wiring).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/lib/Compass.svelte

@@ -15,7 +15,10 @@
   const BOARD_IDS: BoardId[] = ['NW', 'NE', 'SW', 'SE'];
 
   let view = $derived(gameStore.view);
-  let active = $derived(gameStore.activeBoards);
+  // Derive from the reactive `view`, NOT the store's #game getter: #game is
+  // deliberately not a $state proxy, so a $derived reading it never recomputes
+  // and the turn glow/interactivity froze on North after move 1.
+  let active = $derived(PLAYER_BOARDS[view.currentPlayer]);
 
   /** Ghost squares for a given board. */
   function ghostsFor(id: BoardId): Square[] {

src/lib/stores/game.svelte.ts

@@ -3,7 +3,6 @@ import { legalSyncedMoves, selectionHighlight, type SelectionHighlight } from '.
 import { ghosts } from '../../engine/ghosts';
 import { evaluateStatus } from '../../engine/endgame';
 import { serialize, deserialize } from '../../engine/notation';
-import { PLAYER_BOARDS } from '../../engine/boards';
 import type {
   BoardId, Player, Square, SyncMove, HistoryEntry, GhostMarker, GameStatus,
 } from '../../engine/types';
@@ -54,11 +53,6 @@ class GameStore {
     return this.scrubPly !== null;
   }
 
-  /** Which boards belong to the player to move (for the turn glow). */
-  get activeBoards(): [BoardId, BoardId] {
-    return PLAYER_BOARDS[this.#game.currentPlayer];
-  }
-
   /** Grab a piece: must be the current player's turn and a live (non-scrub) view. */
   select(square: Square): void {
     if (this.isScrubbing) return;