feat(provenance): ML stops surfacing the artist category

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_ml_artist_retired.py

@@ -0,0 +1,27 @@
+import pytest
+
+pytestmark = pytest.mark.integration
+
+
+def test_artist_not_surfaced():
+    from backend.app.services.ml.tagger import SURFACED_CATEGORIES
+    assert "artist" not in SURFACED_CATEGORIES
+
+
+def test_artist_not_centroid_eligible():
+    from backend.app.models import TagKind
+    from backend.app.services.ml.centroids import ELIGIBLE_KINDS
+    assert TagKind.artist not in ELIGIBLE_KINDS
+
+
+def test_threshold_for_artist_is_unsurfaced():
+    from backend.app.services.ml.suggestions import SuggestionService
+
+    class _S:
+        suggestion_threshold_character = 0.5
+        suggestion_threshold_copyright = 0.5
+        suggestion_threshold_general = 0.5
+
+    svc = SuggestionService.__new__(SuggestionService)
+    # 'artist' must fall through to the 1.01 "never surfaces" default
+    assert svc._threshold_for(_S(), "artist") == 1.01