feat: migrate browser automation from Playwright MCP to CLI, fix headless setting

Major changes across 21 files (755 additions, 196 deletions):

Browser Automation Migration:
- Add versioned project migration system (prompts.py) with content-based
  detection and section-level regex replacement for coding/testing prompts
- Migrate STEP 5 (browser verification) and BROWSER AUTOMATION sections
  in coding prompt template to use playwright-cli commands
- Migrate STEP 2 and AVAILABLE TOOLS sections in testing prompt template
- Migration auto-runs at agent startup (autonomous_agent_demo.py), copies
  playwright-cli skill, scaffolds .playwright/cli.config.json, updates
  .gitignore, and stamps .migration_version file
- Add playwright-cli command validation to security allowlist (security.py)
  with tests for allowed subcommands and blocked eval/run-code

Headless Browser Setting Fix:
- Add _apply_playwright_headless() to process_manager.py that reads/updates
  .playwright/cli.config.json before agent subprocess launch
- Remove dead PLAYWRIGHT_HEADLESS env var that was never consumed
- Settings UI toggle now correctly controls visible browser window

Playwright CLI Auto-Install:
- Add ensurePlaywrightCli() to lib/cli.js for npm global entry point
- Add playwright-cli detection + npm install to start.bat, start.sh,
  start_ui.bat, start_ui.sh for all startup paths

Other Improvements:
- Add project folder path tooltip to ProjectSelector.tsx dropdown items
- Remove legacy Playwright MCP server configuration from client.py
- Update CLAUDE.md with playwright-cli skill documentation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

agent.py

@@ -240,17 +240,7 @@ async def run_autonomous_agent(
         print_session_header(iteration, is_initializer)
 
         # Create client (fresh context)
-        # Pass agent_id for browser isolation in multi-agent scenarios
-        import os
-        if agent_type == "testing":
-            agent_id = f"testing-{os.getpid()}"  # Unique ID for testing agents
-        elif feature_ids and len(feature_ids) > 1:
-            agent_id = f"batch-{feature_ids[0]}"
-        elif feature_id:
-            agent_id = f"feature-{feature_id}"
-        else:
-            agent_id = None
-        client = create_client(project_dir, model, yolo_mode=yolo_mode, agent_id=agent_id, agent_type=agent_type)
+        client = create_client(project_dir, model, yolo_mode=yolo_mode, agent_type=agent_type)
 
         # Choose prompt based on agent type
         if agent_type == "initializer":