Fix unhandled 'error' event crashes in Node.js process streams - #1929

This PR fixes the node:events:496 throw er; // Unhandled 'error' event ^ crash that was occurring when Node.js process streams emit error events without proper error handlers attached.

Problem

When EventEmitters like process.stdout or process.stdin emit 'error' events without listeners, Node.js throws an unhandled error event causing the entire process to crash with:

node:events:496
      throw er; // Unhandled 'error' event
      ^

Root Cause

Three main sources of unhandled error events were identified:

1. Incomplete error handling in nonInteractiveCli.ts - Only handled EPIPE errors on process.stdout, leaving other error types unhandled
2. Missing error handler in useTerminalSize.ts - Added resize event listener to process.stdout but no error handler
3. No global uncaught exception handler - Only had unhandled promise rejection handler

Solution

Added minimal, surgical error handling:

• Enhanced nonInteractiveCli.ts: Now handles all process.stdout errors, not just EPIPE
• Fixed useTerminalSize.ts: Added error event handler alongside resize listener
• Added global error handler: Comprehensive uncaught exception handler in gemini.tsx

Testing

• ✅ All 424 existing tests pass
• ✅ Manual verification confirms error events are handled gracefully
• ✅ Bundle builds and CLI functionality intact
• ✅ Linting and type checking pass

The fix ensures graceful error handling instead of process crashes while maintaining all existing functionality.

Fixes #1.

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.