[codex] Add symlink flag to fs metadata (#17719)

Add `is_symlink` to FsMetadata struct.

codex-rs/app-server/tests/suite/v2/fs.rs

@@ -89,6 +89,7 @@ async fn fs_get_metadata_returns_only_used_fields() -> Result<()> {
             "createdAtMs".to_string(),
             "isDirectory".to_string(),
             "isFile".to_string(),
+            "isSymlink".to_string(),
             "modifiedAtMs".to_string(),
         ]
     );
@@ -99,6 +100,7 @@ async fn fs_get_metadata_returns_only_used_fields() -> Result<()> {
         FsGetMetadataResponse {
             is_directory: false,
             is_file: true,
+            is_symlink: false,
             created_at_ms: stat.created_at_ms,
             modified_at_ms: stat.modified_at_ms,
         }
@@ -111,6 +113,35 @@ async fn fs_get_metadata_returns_only_used_fields() -> Result<()> {
     Ok(())
 }
 
+#[cfg(unix)]
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn fs_get_metadata_reports_symlink() -> Result<()> {
+    let codex_home = TempDir::new()?;
+    let file_path = codex_home.path().join("note.txt");
+    let symlink_path = codex_home.path().join("note-link.txt");
+    std::fs::write(&file_path, "hello")?;
+    symlink(&file_path, &symlink_path)?;
+
+    let mut mcp = initialized_mcp(&codex_home).await?;
+    let request_id = mcp
+        .send_fs_get_metadata_request(codex_app_server_protocol::FsGetMetadataParams {
+            path: absolute_path(symlink_path),
+        })
+        .await?;
+    let response = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(request_id)),
+    )
+    .await??;
+
+    let stat: FsGetMetadataResponse = to_response(response)?;
+    assert_eq!(stat.is_directory, false);
+    assert_eq!(stat.is_file, true);
+    assert_eq!(stat.is_symlink, true);
+
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn fs_methods_cover_current_fs_utils_surface() -> Result<()> {
     let codex_home = TempDir::new()?;