Jiahao ef186f812a Detach realtime sideband observers without ending the session (#57817) ...

## Why

Stopping a sideband observer should close its WebSocket while preserving the frontend-owned realtime session. The existing frameless session close also sends `session.close`, so observer shutdown needs a transport-only close.

## What changed

- Add `close_transport()` to send a normal WebSocket close without `session.close`.
- Close the sideband transport on cancellation or when the call becomes inactive, including an existing connection awaiting adoption by the input task. Bound the close attempt to five seconds.
- Thread an optional sideband base URL through realtime start processing and allow nested thread ID fields in request serialization scopes.

## Testing

Add WebSocket and core conversation regression tests covering observer detachment for both realtime parsers and conversation versions. Verify that explicit frameless session close still sends `session.close`.

GitOrigin-RevId: 874a8980b0fcd45058e976b00c0d968f5b4b2404

2026-10-28 20:10:15 +00:00

..

clients.rs

Consolidate async header authentication in apply_auth_headers (#57179)

2026-10-26 18:22:11 +00:00

models_integration.rs

Propagate authentication header failures before sending requests (#55607)

2026-10-20 15:43:19 +00:00

realtime_websocket_e2e.rs

Detach realtime sideband observers without ending the session (#57817)

2026-10-28 20:10:15 +00:00

realtime_websocket_tls.rs

Honor configured proxies for realtime WebSocket connections (#47101)

2026-09-21 20:05:21 +00:00

responses_websocket_probe.rs

Preserve WebSocket probe evidence and redact diagnostic details (#57597)

2026-10-27 23:51:43 +00:00

sse_end_to_end.rs

Expose Guardian assessments in response streams (#57757)

2026-10-28 15:04:29 +00:00