Review of #1998. Each reload plan takes a ticket; apply skips a photo a
later-started reload has already been applied to, so an older read that
finishes last no longer restores the previous dimensions and content hash.
The app's background completion now commits through Session::execute_fn,
so the XMP sidecar auto-write (and the save) happen as for the command.
Regression tests: an_older_reload_does_not_replace_a_newer_one,
a_background_reload_writes_the_sidecar_with_auto_write_on.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
photo.reload decoded every targeted file on the UI thread, so a selection
of raws froze the window until all were read. The command is now split into
plan / probe / apply (engine `cmd::reload`); the app intercepts photo.reload
and probes the files on a worker thread with a cancellable activity row
(kind `reload`, counted progress), applying the result as one undo step.
`wait: true` keeps the old in-place behaviour for agents; CLI/MCP unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
