fix(soak): multi-hole round transitions, token refresh, dashboard wiring

- Session loop now handles round_over by clicking #ss-next-btn (the
  scoresheet modal button) instead of exiting early. Waits for next
  round or game_over before continuing.
- SessionPool detects expired tokens on acquire and re-logins
  automatically, writing fresh credentials to .env.stresstest.
- Added 2s post-game delay before goto('/') so the server can process
  game completion before WebSocket disconnect.
- Wired dashboard metrics (games_completed, moves_total, errors),
  activity log entries, and player tiles for both populate and stress
  scenarios.
- Bumped screencast resolution to 960x540 and set headless viewport
  to 960x800 for better click-to-watch framing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/soak/core/screencaster.ts

@@ -59,8 +59,8 @@ export class Screencaster {
     await client.send('Page.startScreencast', {
       format: opts.format ?? 'jpeg',
       quality: opts.quality ?? 60,
-      maxWidth: opts.maxWidth ?? 640,
-      maxHeight: opts.maxHeight ?? 360,
+      maxWidth: opts.maxWidth ?? 960,
+      maxHeight: opts.maxHeight ?? 540,
       everyNthFrame: opts.everyNthFrame ?? 2,
     });
     this.logger.info('screencast_started', { sessionKey });