Update @posthog/agent to 1.12.0

- Bumped to version 1.12.0 with workflow removal changes
- Installed from local tarball

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

Co-Authored-By: Claude <[email protected]>

Author: jonathanlab

package.json

@@ -66,7 +66,7 @@
   "dependencies": {
     "@ai-sdk/openai": "^2.0.52",
     "@phosphor-icons/react": "^2.1.10",
-    "@posthog/agent": "1.10.0",
+    "@posthog/agent": "file:../agent/posthog-agent-1.12.0.tgz",
     "@radix-ui/react-icons": "^1.3.2",
     "@radix-ui/themes": "^3.2.1",
     "@tanstack/react-query": "^5.90.2",