## Summary
- retry ERS `409 environment_offline` responses inside the existing
exec-server recovery loop
- keep all other registry conflicts terminal
- add focused coverage for both cases
## Root cause
When an exec server disconnects and reconnects, the client already
starts recovery and calls ERS `/connect`. During the transient executor
presence gap, ERS can return `409 environment_offline`. The retry
classifier treated every 409 as terminal, so the first response aborted
the existing 25-second recovery window before the executor came back
online. That then caused active processes to be marked lost.
This change classifies only the structured `environment_offline`
conflict as retryable. Recovery continues with the existing bounded
deadline, exponential backoff, and jitter.
## Validation
- `just test -p codex-exec-server client::recovery::tests` — 4 passed
- `just fix -p codex-exec-server` — passed
- `just fmt` — passed
- Full `just test -p codex-exec-server` reached unrelated macOS
filesystem-sandbox integration failures because nested
`/usr/bin/sandbox-exec` is denied in this environment (`sandbox_apply:
Operation not permitted`).
richardopenaiandGitHub
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