Share cached exec-server environment info with Arc (#49798)

## What changed

Return `Arc<EnvironmentInfo>` from `ExecServerClient::environment_info()` so repeated reads and cloned clients share cached metadata without cloning its contents. Wrap metadata from initialization and lazy RPC fetches in `Arc`, while preserving the owned return value in `LazyRemoteExecServerClient`.

## Testing

Extend the cache test to assert pointer identity across cloned clients for both initialization-provided metadata and lazy fetching after connecting to a legacy server.

GitOrigin-RevId: 3f56f4d51a4aebc0c4821c0b128a70efb23933d4

codex-rs/cli/tests/exec_server.rs

@@ -267,7 +267,7 @@ metrics_exporter = {{ otlp-http = {{ endpoint = "{collector_url}/v1/metrics", pr
         prepend_path_dirs: environment_info.prepend_path_dirs.clone(),
         ..EnvironmentInfo::local()
     };
-    assert_eq!(environment_info, expected_info);
+    assert_eq!(environment_info.as_ref(), &expected_info);
     std::fs::remove_file(&manifest)?;
     assert_eq!(client.force_environment_info().await?, expected_info);
 

codex-rs/exec-server/src/client.rs

@@ -290,7 +290,7 @@ struct Inner {
     session_id: OnceLock<String>,
     retired: CancellationToken,
     /// Caches metadata from initialization or the first successful info request for this client's lifetime.
-    environment_info: OnceCell<EnvironmentInfo>,
+    environment_info: OnceCell<Arc<EnvironmentInfo>>,
     reconnect_strategy: Option<ExecServerReconnectStrategy>,
 }
 
@@ -652,7 +652,7 @@ impl HttpClient for LazyRemoteExecServerClient {
 
 impl LazyRemoteExecServerClient {
     pub(crate) async fn environment_info(&self) -> Result<EnvironmentInfo, ExecServerError> {
-        self.get().await?.environment_info().await
+        Ok(self.get().await?.environment_info().await?.as_ref().clone())
     }
 }
 
@@ -827,11 +827,11 @@ impl ExecServerClient {
         self.call(EXEC_METHOD, &params).await
     }
 
-    /// Returns cached executor metadata, fetching it lazily if initialization omitted it.
-    pub async fn environment_info(&self) -> Result<EnvironmentInfo, ExecServerError> {
+    /// Returns shared cached executor metadata, fetching it lazily if initialization omitted it.
+    pub async fn environment_info(&self) -> Result<Arc<EnvironmentInfo>, ExecServerError> {
         self.inner
             .environment_info
-            .get_or_try_init(|| self.force_environment_info())
+            .get_or_try_init(|| async { self.force_environment_info().await.map(Arc::new) })
             .await
             .cloned()
     }
@@ -1292,7 +1292,7 @@ impl ExecServerClient {
             .await?;
         if let Some(info) = initialize_response.environment_info {
             assert!(
-                client.inner.environment_info.set(info).is_ok(),
+                client.inner.environment_info.set(Arc::new(info)).is_ok(),
                 "new client metadata cache must be empty"
             );
         }
@@ -2668,10 +2668,13 @@ mod tests {
         })
         .await?;
 
-        assert_eq!(client.environment_info().await?, expected_info);
+        let info = client.environment_info().await?;
+        assert_eq!(info.as_ref(), &expected_info);
         server.await?;
         // The server is gone, so a cloned client must use the shared cache.
-        assert_eq!(client.clone().environment_info().await?, expected_info);
+        let cached_info = client.clone().environment_info().await?;
+        assert_eq!(cached_info.as_ref(), &expected_info);
+        assert!(Arc::ptr_eq(&info, &cached_info));
         Ok(())
     }