Clean up failed and abandoned marketplace staging directories (#55689)

## Why

Failed marketplace adds can leave temporary checkouts behind, and interrupted adds or upgrades can leave abandoned staging directories.

## What changed

- Share a staging guard across marketplace adds and upgrades so temporary checkouts are removed on completion or failure, including config-write rollback.
- Reclaim up to four abandoned directories per cleanup pass during add and upgrade operations. Use file locks to preserve active checkouts and operating-system-specific names to avoid reclaiming another platform's staging directories.
- Skip symlinks and unrelated entries, and report cleanup failures as warnings.

## Testing

Add regression coverage for failed adds, CLI and automatic-upgrade cleanup, cross-process ownership and abandonment, lock contention, bounded cleanup, and symlink handling.

GitOrigin-RevId: 20999da0eab861dfb8025aad5e9fba2bcaf818b8

codex-rs/utils/path-utils/src/path_utils_tests.rs

@@ -1,7 +1,33 @@
 use super::replace_path_and_deduplicate;
+use super::symlink_metadata_if_exists;
 use pretty_assertions::assert_eq;
 use std::path::Path;
 
+#[test]
+fn symlink_metadata_if_exists_distinguishes_files_directories_and_missing_paths()
+-> std::io::Result<()> {
+    let directory = tempfile::tempdir()?;
+    let file = directory.path().join("file");
+    std::fs::write(&file, "contents")?;
+
+    let directory_metadata =
+        symlink_metadata_if_exists(directory.path())?.expect("directory exists");
+    let file_metadata = symlink_metadata_if_exists(&file)?.expect("file exists");
+    assert_eq!(
+        (directory_metadata.is_dir(), file_metadata.is_file()),
+        (true, true)
+    );
+    assert!(symlink_metadata_if_exists(&directory.path().join("missing"))?.is_none());
+    Ok(())
+}
+
+#[test]
+fn symlink_metadata_if_exists_preserves_io_errors() {
+    let error = symlink_metadata_if_exists(Path::new("invalid\0path"))
+        .expect_err("an invalid path must not be treated as missing");
+    assert_eq!(error.kind(), std::io::ErrorKind::InvalidInput);
+}
+
 #[test]
 fn replace_path_and_deduplicate_preserves_other_paths_and_order() {
     let old_path = Path::new("old");
@@ -22,9 +48,27 @@ fn replace_path_and_deduplicate_preserves_other_paths_and_order() {
 #[cfg(unix)]
 mod symlinks {
     use super::super::resolve_symlink_write_paths;
+    use super::super::symlink_metadata_if_exists;
     use pretty_assertions::assert_eq;
     use std::os::unix::fs::symlink;
 
+    #[test]
+    fn symlink_metadata_if_exists_preserves_links_with_and_without_targets() -> std::io::Result<()>
+    {
+        let directory = tempfile::tempdir()?;
+        let target = directory.path().join("target");
+        let link = directory.path().join("link");
+        std::fs::write(&target, "contents")?;
+        symlink(&target, &link)?;
+
+        let linked_metadata = symlink_metadata_if_exists(&link)?.expect("symlink exists");
+        std::fs::remove_file(target)?;
+        let dangling_metadata = symlink_metadata_if_exists(&link)?.expect("symlink still exists");
+        assert!(linked_metadata.is_symlink());
+        assert_eq!(dangling_metadata.file_type(), linked_metadata.file_type());
+        Ok(())
+    }
+
     #[test]
     fn symlink_cycles_fall_back_to_root_write_path() -> std::io::Result<()> {
         let dir = tempfile::tempdir()?;