Op::SetContent records a photo's file facts (size, dimensions, content hash; undoable).
photo.reload re-probes the photos' files and, for those that changed on disk, updates them and
drops their cached sources; render keys now include the file's content key, so the grid and
loupe re-render. The app reloads this session's external-edit copies whenever its window
regains focus (with a toast).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>