[codex] Observe remote exec-server lifecycle

[richardopenai]

Summary

• Record bounded duration and outcome metrics for remote environment registration and Noise rendezvous connection attempts.
• Count reconnects by bounded reason: disconnect, connection failure, or rejected registration.
• Trace registration at the owning client boundary without exporting raw environment or registration identifiers.
• Replace the stale pre-Noise WebSocket observability design with the current remote transport model.

Stack

Review and land this stack in order:

1. [codex] Trace exec-server JSON-RPC requests #27466 — trace exec-server JSON-RPC requests
2. [codex] Record exec-server lifecycle metrics #27467 — record bounded connection, request, and process lifecycle metrics
3. [codex] Observe remote exec-server lifecycle #27470 — observe remote registration and Noise rendezvous lifecycle (this PR)

Validation

• just test -p codex-exec-server --lib (149 passed)
• just test -p codex-cli --test exec_server (4 passed)
• just argument-comment-lint
• just bazel-lock-check
• just fix -p codex-exec-server -p codex-cli
• just fmt

[chatgpt-codex-connector]

Review source: Codex Cloud Agents (CCA)

Codex Cloud Agents (CCA) couldn't complete this review. The original Codex Review is unaffected.