## Why
A stalled rendezvous WebSocket upgrade can prevent reconnects, while short-lived connections reset reconnect backoff too early. Blocked relay writes also prevent received pongs from clearing their heartbeat deadline.
## What changed
- Bound rendezvous WebSocket connection attempts with `DEFAULT_REMOTE_EXEC_SERVER_CONNECT_TIMEOUT`.
- Retain exponential reconnect backoff across short-lived connections, resetting it only after a connection lasts at least 120 seconds.
- Process pongs during blocked data writes while preserving the in-flight send and its independent write timeout. Prefer queued pongs over an expired heartbeat deadline.
- Abort the relay writer when its owning connection task is dropped.
## Testing
Add coverage for pongs arriving during blocked writes, missing and queued pongs, independent write timeouts, and writer cancellation. Extend reconnect tests to cover stalled WebSocket upgrades without re-registration and backoff reset after a stable session.
GitOrigin-RevId: 0efa350c2b4ada9b89e23df8909063fbb69f33dc
## Why
Remote executors need to recover from confirmed authentication-service outages and spread reconnect attempts after a shared outage. Registration retries must remain limited to confirmed failures before a write, since replaying an ambiguous request can replace a newer registration.
## What changed
- Retry registry responses with HTTP 502 and `authentication_service_unavailable`, alongside the existing HTTP 503 `registration_conflict` retries.
- Accept structured registry errors in `detail`, keeping the canonical `error` authoritative when both are present.
- Randomize reconnect delays between half and all of the current exponential backoff, retaining the 30-second cap.
## Testing
Add coverage for reconnect jitter bounds, authentication-outage retry cancellation, error-envelope precedence, and preservation of Noise identity and initialized sessions across retries. Make the HTTP-header helper cleanup test wait for the helper PID before cancellation and verify process termination when the provider is dropped.
GitOrigin-RevId: 35fdb57732d17b0bbfeca8a4dc557a0988e29a31
Alexi Christakis