test(c2pa): add real FLUX.2 BFL C2PA fixtures (PNG + JPEG)

flux-1.png / flux-1.jpg are real Black Forest Labs FLUX.2 [pro] Playground
outputs (signed C2PA, issuer "Black Forest Labs" + trainedAlgorithmicMedia,
manifests verified to contain no personal data). flux-1.jpg is the first
committed JPEG-with-C2PA fixture, exercising the c2pa-python non-PNG reader path
end to end. Regression tests assert both attribute to "Black Forest Labs (FLUX)".

Also documents the verified finding (n=2, 2026-06-19): BFL's hosted output carries
the signed C2PA manifest but NOT the open invisible-watermark DWT-DCT (decodes to
degenerate all-ones, chance-level vs the FLUX reference) -- the open pixel mark is
dev-inference-code-optional only. So a hosted FLUX.2 image is identified by C2PA
alone, with no open-pixel fallback once C2PA is stripped.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/test_identify.py

@@ -229,6 +229,19 @@ class TestIdentifyRealSamples:
         assert r.is_ai_generated is True
         assert any("IPTC" in w for w in r.watermarks)
 
+    def test_flux_bfl_c2pa_png(self):
+        # flux-1.png: real Black Forest Labs FLUX.2 Playground output (signed C2PA).
+        r = identify(SAMPLES_DIR / "flux-1.png", check_visible=False)
+        assert r.is_ai_generated is True
+        assert r.platform == "Black Forest Labs (FLUX)"
+
+    def test_flux_bfl_c2pa_jpeg_via_reader(self):
+        # flux-1.jpg: same source as a JPEG -- the real committed JPEG-with-C2PA
+        # fixture that exercises the c2pa-python non-PNG reader path end to end.
+        r = identify(SAMPLES_DIR / "flux-1.jpg", check_visible=False)
+        assert r.is_ai_generated is True
+        assert r.platform == "Black Forest Labs (FLUX)"
+
     def test_clean_photo_is_unknown_not_clean(self, clean_photo: Path):
         r = identify(clean_photo, check_visible=False)
         assert r.is_ai_generated is None  # never asserted False