Find Missing Photos took a missing photo's file name with Path::file_name,
which doesn't split on `\` on macOS or Linux, so a library made on Windows
had photos it could only find by content: those with no hash on record
(Lightroom-catalog imports, files edited since) were never found. Both the
missing photos and the files found on disk are now named by one rule: the
part after the last `/` or `\`, in lower case.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>