This fixes two root causes of MCP tool calls hanging indefinitely:
1. Transform ensureValidJson from validator to transformer
- Previously threw errors on undefined values, causing handlers to crash
- Now converts undefined→null, Date→ISO string, bigint→string, etc.
- Ensures all MCP handlers always return valid JSON responses
2. Cancel waitTracker when interrupting agents
- Added waitTracker.cancel() in cancel_agent handler
- Added waitTracker.cancel() in kill_agent handler
- Resolves waiting wait_for_agent promises when agents are interrupted
- Prevents indefinite hangs requiring server restart
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
