feat: MBTarget exposes rgMbid + artistMbid from the resolver

worker/tests/test_musicbrainz_live.py

@@ -16,3 +16,5 @@ def test_live_resolves_continuum():
     assert target.track_count and target.track_count >= 10  # Continuum has 12 tracks
     assert "continuum" in target.album.casefold()
     assert target.year == 2006
+    assert target.rg_mbid  # a real release-group MBID
+    assert target.artist_mbid  # a real artist MBID

worker/tests/test_types_mbtarget.py

@@ -0,0 +1,8 @@
+from lyra_worker.types import MBTarget
+
+
+def test_mbtarget_has_rg_and_artist_mbid_defaults():
+    t = MBTarget(artist="A", album="B")
+    assert t.rg_mbid == "" and t.artist_mbid == ""
+    t2 = MBTarget(artist="A", album="B", rg_mbid="rg1", artist_mbid="a1")
+    assert t2.rg_mbid == "rg1" and t2.artist_mbid == "a1"