fix(web-e2e): expose serialize() on classic bridge; use real clock API

Two latent test bugs surfaced once the e2e suite actually ran (it had been
red on the webServer startup timeout, so these never executed): 14 passed,
4 failed.

- game.js `__FERROUS_DEBUG__` was missing `serialize()` — play.html's bridge
  has it but the /play-classic bridge (which the resume/move-history tests
  use) drifted. Added it (the wasm SolitaireGame already exposes serialize()).
- game_behaviors.spec.js called `page.clock.tick()`, which is the sinon name;
  Playwright's Clock API method is `page.clock.runFor()`. Replaced all 6 calls.

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

solitaire_server/web/game.js

@@ -986,6 +986,9 @@ window.__FERROUS_DEBUG__ = {
     snapshot() {
         return game ? game.debug_snapshot() : null;
     },
+    serialize() {
+        return game ? game.serialize() : null;
+    },
     applyLegalMove(index) {
         if (!game) return { ok: false, error: "game_not_ready" };
         const result = game.debug_apply_legal_move(index);