[BUG] Desktop app (macOS): Files panel file tree does not refresh when Claude creates a new file

Description

When Claude creates a new file with the Write tool while the Files panel is open, the new file does not appear in the panel's file tree. The panel keeps showing the directory listing as it was when the panel was opened. Closing the panel and reopening it shows the file correctly.

This looks like the same class of staleness as #52740 (diff viewer shows stale content after Claude edits files), but it affects the file tree listing rather than the contents of an already open file.

Steps to reproduce

1. Open a session with a working directory containing a few files.
2. Open the Files panel and leave it open.
3. Ask Claude to create a new file in that directory (Write tool).
4. Observe the Files panel. The new file is not listed.
5. Close the Files panel and reopen it. The new file is now listed.

Expected behavior

The file tree reflects filesystem changes made during the session without requiring the panel to be closed and reopened.

Actual behavior

The file tree is only populated when the panel is opened and is not updated afterwards.

Notes

• The file itself is written correctly. Verified on disk with ls -la immediately after the Write call, so this is a UI refresh issue and not the write failure described in #40227.
• Reproduced twice in the same session, with two different files in the same directory.
• Not caused by an unusual path. First observed in a directory whose name ended with a space, and reproduced after renaming the directory to remove it.
• The file was not dot-prefixed, so #53519 does not apply.

Environment

• macOS 27.0 (Apple silicon)
• Claude desktop app 1.24012.9
• Claude Code 2.1.220