Merge feat/unknown-album: default blank album to 'Unknown Album'

Downloads with no album (regular YouTube videos, fan edits, etc) left a blank
album, which trips up players like Plexamp. yt_download now appends
--parse-metadata "%(album|Unknown Album)s:%(meta_album)s" so the native/resolved
album is kept when present, else 'Unknown Album' is embedded. Applies to all
download paths (search, playlist, single URL).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

musicfetch

@@ -618,6 +618,9 @@ def yt_download(url_or_query: str, target_folder: Optional[str], quality: str, d
             cmd += ["--parse-metadata", f"{hit.title}:%(title)s"]
         if hit.year:
             cmd += ["--parse-metadata", f"{hit.year}:%(release_year)s"]
+    # Always embed an album: the resolved/native album if present, else a
+    # placeholder so players (e.g. Plexamp) don't choke on a blank album.
+    cmd += ["--parse-metadata", "%(album|Unknown Album)s:%(meta_album)s"]
     cmd.append(url_or_query)
 
     dest = outtmpl or target_folder

server/requirements.txt

@@ -4,3 +4,4 @@ requests
 ytmusicapi
 rich
 yt-dlp
+mutagen

tests/test_playlist.py

@@ -102,3 +102,11 @@ def test_yt_download_returns_true_on_zero_exit(monkeypatch):
 
 def test_yt_download_dry_run_returns_true():
     assert mf.yt_download("u", "/tmp/x", "best", True) is True
+
+
+def test_yt_download_always_sets_album_default(monkeypatch):
+    captured = {}
+    monkeypatch.setattr(mf.os, "makedirs", lambda *a, **k: None)
+    monkeypatch.setattr(mf.subprocess, "run", lambda cmd, **k: captured.update(cmd=cmd) or _CP(""))
+    mf.yt_download("u", "/tmp/x", "best", False)
+    assert "%(album|Unknown Album)s:%(meta_album)s" in captured["cmd"]