feat(metadata): read EXIF Make tag; collect Ideogram/Recraft/Krea-FLUX

Collected live samples from three popular generators we lacked:

- Ideogram tags its downloads with EXIF Make="Ideogram AI" (no C2PA, no
  SynthID, no imwatermark) -- the Make tag is its only signal. exif_generator
  only read Software/Artist/ImageDescription, so it missed this; now reads
  Make too. Real cameras put "Apple"/"Canon" in Make (no AI token), so this
  stays low-false-positive. 4 originals ingested.
- Recraft (PNG export) and Krea hosting FLUX 2: downloads carry NO detectable
  signal -- no C2PA/EXIF/IPTC, and notably no imwatermark despite Krea running
  FLUX. identify correctly reports 'unknown'. Both ingested as neg fixtures.

Lesson recorded in CLAUDE.md: the imwatermark detector fires only on pristine
output from a pipeline that runs the encoder (diffusers default, official BFL),
not from re-hosts (Krea/Stability) or re-encoded exports (Recraft/Canva).

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

tests/test_metadata.py

@@ -362,6 +362,21 @@ class TestExifGenerator:
         path = _img_with_software(tmp_path, "jpg", "Adobe Photoshop 25.0")
         assert exif_generator(path) is None
 
+    def test_make_tag_ai_tool_detected(self, tmp_path: Path):
+        # Ideogram tags its output with EXIF Make="Ideogram AI" (verified on a
+        # real download), so the Make tag must be read too.
+        exif = piexif.dump({"0th": {piexif.ImageIFD.Make: b"Ideogram AI"}, "Exif": {}, "GPS": {}, "1st": {}})
+        path = tmp_path / "ideogram.jpg"
+        Image.new("RGB", (64, 64)).save(path, exif=exif)
+        assert exif_generator(path) == "Ideogram AI"
+
+    def test_camera_make_not_flagged(self, tmp_path: Path):
+        # A real camera Make ("Apple") carries no AI token -> not flagged.
+        exif = piexif.dump({"0th": {piexif.ImageIFD.Make: b"Apple"}, "Exif": {}, "GPS": {}, "1st": {}})
+        path = tmp_path / "iphone.jpg"
+        Image.new("RGB", (64, 64)).save(path, exif=exif)
+        assert exif_generator(path) is None
+
     def test_xmp_creatortool_scan_covers_unopenable(self, tmp_path: Path):
         # PIL can't open this fake HEIF; the raw XMP CreatorTool scan still works.
         path = tmp_path / "fake.heic"