feat(KB-032): add Planning Mode for AI-assisted task creation

- Add PlanningModeModal component with interactive task planning UI
- Implement backend planning API with /api/planning endpoints
- Add PlanningSession class for managing planning state
- Integrate planning mode into dashboard with header button
- Add comprehensive tests for planning components and API routes
- Include AI agent structure for future planning automation
- Update README with Planning Mode documentation

packages/dashboard/package.json

@@ -32,6 +32,7 @@
     "@codemirror/theme-one-dark": "^6.1.2",
     "@codemirror/view": "^6.36.4",
     "@kb/core": "workspace:*",
+    "@kb/engine": "workspace:*",
     "@types/multer": "^2.1.0",
     "express": "^5.1.0",
     "lucide-react": "^1.7.0",