feat: Complete Phase 4 - Remove legacy JavaScript files

Phase 4 Complete: Cleanup legacy files after successful migration

Removed Files (29 total):
- /markitect/static/js/ directory (entire directory deleted)
  * Core modules: debug-system.js, section-manager.js
  * Components: debug-panel.js, dom-renderer.js, document-controls.js
  * Configuration: config-loader.js
  * Main files: main.js, main-updated.js
  * Plugins: document-navigator-plugin.js
  * Widgets: UIWidget.js, Widget.js, DocumentNavigator.js
  * Test files: All test JS files and test HTML/MD files
- /markitect/static/editor.js (unused legacy file)

Preserved:
- /markitect/static/css/ (still referenced in templates)

Migration Impact:
- ✅ Single source of truth: All JavaScript now in /capabilities/testdrive-jsui/js/
- ✅ No duplicate files in codebase
- ✅ Clean separation: Capability is authoritative location
- ✅ All tests still passing (84 automated tests)
- ✅ Main app rendering verified (view & edit modes)

Migration Status:
- Phase 1: ✅ Complete (files copied to capability)
- Phase 2: ⏭️ Skipped (comprehensive testing in Phase 1)
- Phase 3: ✅ Complete (templates updated)
- Phase 4: ✅ Complete (legacy files removed)

🎉 MIGRATION FULLY COMPLETE - All phases done

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

capabilities/testdrive-jsui

@@ -1 +1 @@
-Subproject commit 891d78553391928fac5230de2d6fae1e9a25af65
+Subproject commit f5ce02cf8d8ad38fce77fa70b266216340bc4489