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>
Remove the Load Snapshots button. Snapshots are fetched
automatically when both target and remote have values,
triggered by Select.Changed events.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>