WebSocket endpoint for interactive query debugging.

IMPORTANT: This endpoint uses WebSocket protocol, which is not fully supported by OpenAPI 3.0 generators. Generated clients will only handle the HTTP upgrade handshake but will NOT provide WebSocket communication methods. Clients must implement WebSocket handling manually.

Protocol:

1. Client connects via WebSocket to /v1/debug
2. Client sends a QuerySpecDto as a JSON text message
3. Server streams back ResultEventDto objects as JSON text messages
4. Connection remains open until client disconnects or query is terminated

Note for Client Implementers: You will need to use a WebSocket library directly for this endpoint. The generated client code will not be sufficient for full functionality.