sync: Agent Architecture Overhaul - AI SDK 6 + workflow optimization

Synced from private repo (feature/ai-sdk-6-upgrade):
- Upgrade AI SDK 5 → 6 (packages + API changes)
- Add sqliteQuery tool for flexible read-only queries
- New WorkflowExecutor with workflow-specific tools
- 83% token reduction for workflow execution
- Remove mini-rah dead code (simplified architecture)
- Add context management usage endpoint
- Fix Connect workflow instructions
- Clickable node references in workflow UI

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

package.json

@@ -21,16 +21,16 @@
     "evals": "RAH_EVALS_LOG=1 tsx tests/evals/runner.ts"
   },
   "dependencies": {
-    "@ai-sdk/anthropic": "^2.0.27",
-    "@ai-sdk/openai": "^2.0.22",
-    "@ai-sdk/react": "^2.0.26",
-    "@langchain/core": "^0.3.0",
-    "@langchain/textsplitters": "^0.1.0",
+    "@ai-sdk/anthropic": "^3.0.9",
+    "@ai-sdk/openai": "^3.0.7",
+    "@ai-sdk/react": "^3.0.29",
+    "@langchain/core": "^1.0.1",
+    "@langchain/textsplitters": "^1.0.1",
     "@radix-ui/react-checkbox": "^1.1.1",
     "@radix-ui/react-dropdown-menu": "^2.1.1",
     "@radix-ui/react-label": "^2.1.0",
     "@radix-ui/react-slot": "^1.1.0",
-    "ai": "^5.0.68",
+    "ai": "^6.0.27",
     "better-sqlite3": "^12.2.0",
     "cheerio": "^1.1.2",
     "class-variance-authority": "^0.7.0",
@@ -41,8 +41,8 @@
     "openai": "^4.103.0",
     "pdf-parse": "^1.1.1",
     "pdfjs-dist": "^5.4.296",
-    "react": "19.0.0",
-    "react-dom": "19.0.0",
+    "react": "^19.0.1",
+    "react-dom": "^19.0.1",
     "tailwind-merge": "^2.5.2",
     "uuid": "^11.1.0",
     "youtube-captions-scraper": "^2.0.3",