feat: hard negative source_model tracking, training toggle

Add source_model column to hard_negatives table with migration. New
get_hard_negatives() returns full rows, delete_hard_negatives_by_ids()
for bulk deletion. get_training_data() gains use_hard_negatives param.
TrainDialog has "Use hard negatives" checkbox. Scan panel passes current
model name when marking negatives.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_db.py

@@ -50,3 +50,60 @@ def test_scan_result_history():
         assert len(results.get("MODEL_A", [])) == 1
     finally:
         os.unlink(path)
+
+
+def test_hard_negatives_source_model():
+    """Hard negatives should store source_model."""
+    with tempfile.NamedTemporaryFile(suffix=".db", delete=False) as f:
+        path = f.name
+    try:
+        db = ProcessedDB(path)
+        db.add_hard_negatives("a.mp4", "test", [10.0, 20.0],
+                              source_path="/a.mp4", source_model="HUBERT_XLARGE")
+        rows = db.get_hard_negatives("test")
+        assert len(rows) == 2
+        assert all(r["source_model"] == "HUBERT_XLARGE" for r in rows)
+    finally:
+        os.unlink(path)
+
+
+def test_training_data_skips_hard_negatives():
+    """get_training_data with use_hard_negatives=False should skip them."""
+    with tempfile.NamedTemporaryFile(suffix=".db", delete=False) as f:
+        path = f.name
+    try:
+        db = ProcessedDB(path)
+        # Create a source file that "exists" — use the temp db file itself
+        db.add("a.mp4", 10.0, "/out/folder/g/clip.mp4", profile="test",
+               source_path=path)
+        db.add_hard_negatives("a.mp4", "test", [500.0], source_path=path)
+        # With hard negatives
+        data_with = db.get_training_data("test", "folder", use_hard_negatives=True)
+        # Without hard negatives
+        data_without = db.get_training_data("test", "folder", use_hard_negatives=False)
+        assert len(data_with) >= 1
+        # The "with" case should have the hard negative time in neg list
+        neg_with = sum(len(vi[3]) for vi in data_with)
+        neg_without = sum(len(vi[3]) for vi in data_without)
+        assert neg_with > neg_without, "hard negatives should be excluded when use_hard_negatives=False"
+    finally:
+        os.unlink(path)
+
+
+def test_delete_hard_negatives_by_ids():
+    """delete_hard_negatives_by_ids should remove specific rows."""
+    with tempfile.NamedTemporaryFile(suffix=".db", delete=False) as f:
+        path = f.name
+    try:
+        db = ProcessedDB(path)
+        db.add_hard_negatives("a.mp4", "test", [10.0, 20.0, 30.0],
+                              source_path="/a.mp4")
+        rows = db.get_hard_negatives("test")
+        assert len(rows) == 3
+        # Delete first two
+        db.delete_hard_negatives_by_ids([rows[0]["id"], rows[1]["id"]])
+        remaining = db.get_hard_negatives("test")
+        assert len(remaining) == 1
+        assert remaining[0]["start_time"] == 30.0
+    finally:
+        os.unlink(path)