Bump react (internal) (#1893)

<!-- CURSOR_SUMMARY -->
> [!NOTE]
> Upgrade React and React DOM to 19.2.1 and align related lockfile
entries (including scheduler).
> 
> - **Dependencies**:
> - Upgrade `react` to `^19.2.1` and `react-dom` to `^19.2.1` in
`package.json`.
> - Update lockfile resolutions for `react`, `react-dom`, and
`scheduler` (`0.27.0`), including peer/dependency ranges.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
7085cd54e499a04e89f6325f4e274e19cdde4961. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Upgraded React and React DOM to 19.2.1 to adopt the latest fixes. No app
code changes.

- **Dependencies**
  - Bumped react and react-dom to ^19.2.1.
  - Updated scheduler to 0.27.0 via react-dom.

<sup>Written for commit 7085cd54e499a04e89f6325f4e274e19cdde4961.
Summary will update automatically on new commits.</sup>

<!-- End of auto-generated description by cubic. -->

package.json

@@ -152,8 +152,8 @@
     "monaco-editor": "^0.52.2",
     "openai": "^4.91.1",
     "posthog-js": "^1.236.3",
-    "react": "^19.0.0",
-    "react-dom": "^19.0.0",
+    "react": "^19.2.1",
+    "react-dom": "^19.2.1",
     "react-markdown": "^10.1.0",
     "react-resizable-panels": "^2.1.7",
     "react-shiki": "^0.5.2",