[codex] Observe remote exec-server lifecycle (#27470)

## 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. #27466 — trace exec-server JSON-RPC requests
2. #27467 — record bounded connection, request, and process lifecycle
metrics
3. #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`

codex-rs/cli/src/main.rs

@@ -1706,7 +1706,10 @@ async fn run_exec_server_command(
             remote_config.name = name;
         }
         let remote_config = remote_config.with_telemetry(telemetry);
-        codex_exec_server::run_remote_environment(remote_config, runtime_paths).await?;
+        exec_server_telemetry::run_until_shutdown(async move {
+            codex_exec_server::run_remote_environment(remote_config, runtime_paths).await
+        })
+        .await?;
         Ok(())
     } else {
         let config_result = load_exec_server_config(root_config_overrides, strict_config).await;
@@ -1718,11 +1721,12 @@ async fn run_exec_server_command(
         let (_otel, telemetry) = exec_server_telemetry::init(config.as_ref());
         let listen_url = cmd
             .listen
-            .as_deref()
-            .unwrap_or(codex_exec_server::DEFAULT_LISTEN_URL);
-        codex_exec_server::run_main_with_telemetry(listen_url, runtime_paths, telemetry)
-            .await
-            .map_err(anyhow::Error::from_boxed)
+            .unwrap_or_else(|| codex_exec_server::DEFAULT_LISTEN_URL.to_string());
+        exec_server_telemetry::run_until_shutdown(async move {
+            codex_exec_server::run_main_with_telemetry(&listen_url, runtime_paths, telemetry).await
+        })
+        .await
+        .map_err(anyhow::Error::from_boxed)
     }
 }