Select a snapshot and click Browse Files to see all files in that
snapshot on the remote. Also adds 'gniza snapshots browse' CLI command.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Replace `is Select.BLANK` / `is not Select.BLANK` with isinstance
checks, as the sentinel identity varies across Textual versions.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>