Remove unused gateway endpoints for watch app

[maxonary]

Issue

The /v1/chat/completions HTTP endpoint is no longer used by the watch app (switched to WebSocket realtime). Should be cleaned up or documented as legacy.

Current State

• HTTP endpoint still exists in gateway
• Watch app uses WebSocket /v1/realtime instead
• Dead code taking up maintenance burden
• Confusing for future developers

Options

1. Remove Entirely

   • Delete endpoint from server.ts
   • Remove related tests
   • Clean up any supporting code

2. Document as Legacy

   • Add comment explaining it was replaced
   • Mark as deprecated
   • Note when it will be removed

3. Keep for Compatibility

   • If other apps still use it
   • Add deprecation warning
   • Plan removal timeline

Recommendation

Remove entirely since watch app is the primary client.