fix(fc3c): structured JPEGs + phash_threshold=0 so both fixtures attach

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

tests/test_download_service.py

@@ -34,10 +34,26 @@ async def seed_artist_and_source(db, db_sync):
     return artist, source
 
 
-def _make_jpg(path: Path, color=(100, 100, 100)):
+def _make_jpg(path: Path, split: str = "h"):
+    """Write a structured JPEG so phash isn't degenerate.
+
+    Solid-color images all phash-collapse (DCT of a flat image is zero).
+    Use `split='h'` (top/bottom halves) or `split='v'` (left/right) to
+    give each fixture file a distinct phash.
+    """
     from PIL import Image
     path.parent.mkdir(parents=True, exist_ok=True)
-    Image.new("RGB", (32, 32), color).save(path, "JPEG")
+    im = Image.new("RGB", (64, 64), (255, 255, 255))
+    px = im.load()
+    if split == "h":
+        for y in range(32):
+            for x in range(64):
+                px[x, y] = (0, 0, 0)
+    else:  # 'v'
+        for y in range(64):
+            for x in range(32):
+                px[x, y] = (0, 0, 0)
+    im.save(path, "JPEG")
 
 
 def _make_fake_dl_result(
@@ -90,9 +106,11 @@ async def test_download_source_attaches_written_files(
     images_root = tmp_path / "images"
     f1 = images_root / "alice" / "patreon" / "post" / "a.jpg"
     f2 = images_root / "alice" / "patreon" / "post" / "b.jpg"
-    # Distinct colors → distinct sha256 → both attach (not deduped).
-    _make_jpg(f1, color=(200, 50, 50))
-    _make_jpg(f2, color=(50, 50, 200))
+    # Structured h/v split → distinct sha256 AND distinct phash;
+    # also pin phash_threshold=0 so even tiny perceptual similarity
+    # between the two doesn't trigger duplicate_phash.
+    _make_jpg(f1, split="h")
+    _make_jpg(f2, split="v")
 
     fake_gdl = _fake_gdl_with_result(_make_fake_dl_result(
         success=True,
@@ -104,6 +122,7 @@ async def test_download_source_attaches_written_files(
     sync_settings = db_sync.execute(
         select(ImportSettings).where(ImportSettings.id == 1)
     ).scalar_one()
+    sync_settings.phash_threshold = 0  # only exact phash collisions dedup
 
     importer = Importer(
         session=db_sync, images_root=images_root,