Fix real-time output clearing for collaborative editing

[ellisonbg]

Summary

Fixes the real-time synchronization issue where clearing cell outputs in a collaborative notebook session only affected the local user. Other connected users would continue to see the outputs until they reloaded the notebook.

Problem

The current implementation in PR #147 clears outputs from disk storage but doesn't update the shared YDoc that powers real-time collaboration between multiple users.

Solution

Reversed the order of operations in the output clearing process:

1. FIRST: Clear outputs from YDoc immediately → All users see the change instantly
2. SECOND: Make API call to clear disk storage → Ensures persistence

Key Changes

• Added sharedCodeCell.setOutputs([]) before the API call
• Improved error handling with early returns
• Enhanced logging to distinguish between YDoc and disk operations
• Maintains backward compatibility with existing API

Testing

• ✅ Single user: Output clearing works as before
• ✅ Multiple users: All connected clients see cleared outputs immediately
• ✅ Network failures: Real-time collaboration works even if disk API fails
• ✅ Error handling: Graceful degradation with proper error logging

Technical Details

The frontend already observes YDoc outputsChange events (lines 40-75 in notebook-factory.ts), so clearing the shared model automatically triggers UI updates across all connected clients.

This approach follows the same pattern used for adding outputs in real-time and provides better user experience with instant feedback.

[ellisonbg]

@Zsailer @3coins revision of #147

[ellisonbg]

Ping @3coins for review

[3coins]

@ellisonbg
Thanks for submitting this fix. Looks good, there is a build error that requires a lint fix, but ok otherwise. I ran lint locally, but wasn't able to push because your fork doesn't exist anymore.