Version 2.0.0: Animation fixes, timing improvements, and E2E test suite

Animation fixes:
- Fix held card positioning bug (was appearing at bottom of page)
- Fix discard pile blank/white flash on turn transitions
- Fix blank card at round end by skipping animations during round_over/game_over
- Set card content before triggering flip animation to prevent flash
- Center suit symbol on 10 cards

Timing improvements:
- Reduce post-discard delay from 700ms to 500ms
- Reduce post-swap delay from 1800ms to 1000ms
- Speed up swap flip animation from 1150ms to 550ms
- Reduce CPU initial thinking delay from 150-250ms to 80-150ms
- Pause now happens after swap completes (showing result) instead of before

E2E test suite:
- Add Playwright-based test bot that plays full games
- State parser extracts game state from DOM for validation
- AI brain ports decision logic for automated play
- Freeze detector monitors for UI hangs
- Visual validator checks CSS states
- Full game, stress, and visual test specs

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/e2e/.gitignore

@@ -0,0 +1,5 @@
+node_modules/
+playwright-report/
+test-results/
+*.db
+*.db-journal