fix: use official ext-apps useApp hook to fix blank MCP App rendering (#578)

The custom useToolData hook had lifecycle issues that prevented the UI
from rendering in Claude Desktop/web: no appInfo in App constructor,
unhandled connect() Promise, app.close() on unmount conflicting with
React Strict Mode. Switched to the official useApp hook from
@modelcontextprotocol/ext-apps/react which handles initialization
handshake, handler registration, and cleanup correctly.

Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

CHANGELOG.md

@@ -7,6 +7,18 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [2.34.4] - 2026-02-07
+
+### Fixed
+
+- **MCP Apps: Fix blank UI rendering in Claude**: Rewrote `useToolData` hook to use the official `useApp` hook from `@modelcontextprotocol/ext-apps/react` instead of manually managing `App` lifecycle
+  - Proper initialization handshake with host via `appInfo` and `capabilities`
+  - Handlers registered via `onAppCreated` callback (before `connect()`) to avoid race conditions
+  - Removed `app.close()` on unmount which caused issues with React Strict Mode
+  - Added visible error and connection states with inline colors for debugging
+
+Conceived by Romuald Czlonkowski - https://www.aiadvisors.pl/en
+
 ## [2.34.3] - 2026-02-07
 
 ### Fixed