#445 fix(desktop): ensure Monaco editor loads syntax highlighting reliably

Summary

• Fix race condition where Monaco editor would render before theme was registered
• Add useMonacoReady hook to allow components to wait for Monaco initialization
• DiffViewer now properly waits for Monaco to be ready before rendering

Problem

When opening files in the diff viewer, syntax highlighting would sometimes not load immediately. This was caused by:

1. MonacoProvider rendering children immediately without waiting for Monaco initialization
2. Theme definition happening asynchronously via monacoPromise.then(), but DiffEditor already trying to use SUPERSET_THEME before it was registered
3. Theme store starting with monacoTheme: null until hydration, causing the first render to skip theme registration

Solution

• Added MonacoContext with isReady state to track full initialization
• Provider now waits for both Monaco initialization AND theme availability before setting isReady: true
• Exposed useMonacoReady() hook for consumers to check readiness
• DiffViewer uses the hook to show loading state until Monaco is fully ready

Test plan

• Open a file in the diff viewer
• Verify syntax highlighting loads immediately (no delay/flicker)
• Switch between files and verify highlighting persists
• Change theme and verify editor updates correctly

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Improved Monaco editor initialization handling by adding a readiness check before rendering the diff viewer. Users will now see a loading state while the editor initializes, preventing potential rendering issues during startup.

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