Two-part fix for "[Unknown Album]" vs "Singles" mismatch that broke the
metadata editor (File not found):
- Download: always write an album tag, defaulting to "Singles" so it matches
the on-disk folder (album || 'Singles'). No-album tracks no longer show as
"[Unknown Album]" while living in a "Singles" folder. (Future downloads.)
- Editor resolve: Subsonic getSong returns a *virtual* tag-built path (e.g.
"[Unknown Album]/Title.mp3" with raw "|"), not the physical file ("Singles/
Artist - Title_YTPMV.mp3"). Add findExistingTrack as a final fallback, and
make its normalizer map the sanitized chars (/ \ : * ? " < > | and _) to a
space so a title tag matches the sanitized filename. (Fixes existing tracks.)
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>