## Why
Rendezvous connection warnings report only a generic WebSocket error, while debug logs include raw error text. Structured diagnostics make failures easier to investigate without logging potentially sensitive error payloads.
## What changed
- Generate a request ID for each connection attempt, send it as `x-request-id`, and include it in the connection span and connection, disconnection, and failure logs alongside the attempt count.
- Replace raw error logging with typed error categories, I/O error kinds, HTTP status codes, and allowlisted values from `x-codex-rendezvous-rejection-reason`.
- Ignore unknown rejection reasons and response bodies.
## Testing
Add tests for rejection-header allowlisting, typed I/O failures, and a rejected WebSocket handshake that verifies the request ID header and preserves the HTTP status and known rejection reason.
GitOrigin-RevId: a8274fec965bcf5b8453b047c0bb79396cdf6ba4
