Description

Release 2. If an open file changes on disk while editing (synced vault: Obsidian/iCloud), glint silently overwrites on save. Track the file's mtime/size at load; before saving, if it changed, warn and offer to overwrite/reload/diff instead of clobbering.

Acceptance Criteria

• #1 Detect when the open file changed on disk since load
• #2 On save with an external change, warn instead of silently overwriting