feat: UI improvements and E2E testing with agent-browser

- Move font controls (A+/A-) to left of connection status
- Redesign tab count with stepper buttons (−/number/+)
- Remove respawn panel, integrate settings into session options modal
- Fix Monitor panel SSE handler (wrong element ID)
- Add screen wrapping support to Session class
- Add E2E testing skill using agent-browser
- Document testing approach in README.md and CLAUDE.md

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

package.json

@@ -37,6 +37,7 @@
     "@types/node": "^20.14.0",
     "@types/uuid": "^10.0.0",
     "@vitest/coverage-v8": "^4.0.17",
+    "agent-browser": "^0.6.0",
     "tsx": "^4.15.0",
     "typescript": "^5.5.0",
     "vitest": "^4.0.17"