## Why
Synchronous auth header construction could silently return no credentials when managed authentication became unavailable. Callers need an error to avoid sending requests with missing or partial authentication.
## What changed
- Make `AuthProvider::add_auth_headers`, `to_auth_headers`, and auth header telemetry fallible, and propagate failures through request and WebSocket setup.
- Return a transient error when managed authentication is unavailable, and preserve network policy denials through auth error conversion.
- Retry transient MCP authentication errors while treating build errors and policy denials as terminal.
- Cancel local MCP event streams before resolving authentication so cleanup still works when credentials become unavailable.
## Testing
Add regression coverage for rejected partial authentication, async header resolution, terminal auth errors without sending requests, managed account changes, MCP retry classification, and local stream cancellation after authentication becomes unavailable.
GitOrigin-RevId: 39d981e232cba1e302de502a2fa6239101114ed1
## What changed
- Move the reusable WebSocket relay, registration, frame capture, and encryption assertion helpers into `codex-exec-server-test-support`.
- Re-export the helpers from the existing relay test module so its callers keep the same interface.
- Add the Cargo dependencies and Bazel proto compile data required by the shared support module.
GitOrigin-RevId: 0383149c79ef86cb5e64a09baec41332f9eec4c6
## What changed
- Add a `NoiseStreamHandler` abstraction that owns payload encoding, decoding,
and connection processing while the virtual stream handles framing,
encryption, and multiplexing.
- Reassemble authenticated payloads as opaque bytes, with the existing
JSON-RPC processor supplied as a handler implementation.
- Have the physical relay send a reset after the current stream instance
closes, including when its processor exits before the writer task.
## Testing
- Verify local JSON-RPC decoding creates the queued request span before queue
admission.
- Verify a processor exit resets the corresponding Noise harness stream.
GitOrigin-RevId: 270befcc8bfbf27e46c84d6a2c6e349cb98ea3f8
cooper-oai