Expose environment status through app-server (#32920)

## What changed

- Add the experimental `environment/status` request for inspecting a configured environment without starting or reconnecting it.
- Report `ready`, `pending`, `disconnected`, or `unknown`, including error details for disconnected and unknown environments.
- Probe ready remote environments over their existing exec-server connection.

## Testing

- Add an app-server integration test covering local and remote ready, pending, disconnected, and unknown environments.

GitOrigin-RevId: 397bba603aa9e0b59008ee6cb7cbde46e357652c

codex-rs/app-server-protocol/src/export.rs

@@ -45,6 +45,7 @@ const IGNORED_DEFINITIONS: &[&str] = &["Option<()>"];
 const JSON_V1_ALLOWLIST: &[&str] = &["InitializeParams", "InitializeResponse"];
 const EXPERIMENTAL_CLIENT_METHOD_DEPENDENCY_TYPES: &[&str] = &[
     "EnvironmentShellInfo",
+    "EnvironmentStatusKind",
     "PathUri",
     "RemoteControlClient",
     "RemoteControlClientsListOrder",