Align watermark content with detector coverage

scripts/assets/visible-mark-candidates/README.md

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+# Unregistered visible-mark candidates
+
+Synthetic detection silhouettes for marks that are measured but NOT registered:
+none of these separates its positives from clean negatives yet, so shipping them
+would attribute and fill corners on content that carries no mark (a false fill
+is the worse error). Assets are regenerated by
+`scripts/render_vendor_silhouettes.py`; a candidate is deleted from here on the
+day its mark registers (the asset moves to the package `assets/`).
+
+Measurements below are local calibration snapshots. Candidate pools are
+provenance cohorts, not automatically visible-mark positives; comparison controls
+are independently selected no-signal images and are not adjudicated negatives.
+Each needs capture-solved alphas or vendor-accurate font work before it can
+ship; `scripts/vendor_mark_calibrate.py` is the candidate-detector harness.
+
+| Asset | Mark | Evidence | Result |
+| --- | --- | --- | --- |
+| `samsung_en_alpha.png` | Samsung Galaxy AI label, English locale ("AI-generated content", bottom-left) | 5 corpus files | POS 0.11-0.30 vs NEG max 0.40 (binary); tophat/gray tried, no separation. The registered Italian engine scores 0.18-0.31 on the same files -- same layout class, wrong glyph template. |
+| `gemini_text_alpha.png` | "Generated with Gemini" text label (bottom-right; the registered gemini mark is the sparkle icon) | 3 corpus files | POS 0.07-0.22 vs NEG max 0.32; coverage gate finds the blob (0.29-0.35) but the Arial silhouette misses Google's letterforms. |
+| `notebooklm_alpha.png` | NotebookLM wordmark (bottom-right) | 12 corpus files | locate geometry not yet fitted; POS max 0.12. |
+| `dola_alpha.png` | DolaAI on images (the video mark is registered) | 12 corpus files | POS 0.11-0.21 vs NEG max 0.30. |
+| `mindvideo_alpha.png` | MindVideo.AI (top-right) | 11 corpus files | POS 0.29-0.32 vs NEG max 0.30 -- borderline overlap, not shippable. |
+| `xinghui_alpha.png` | 星绘AI生成 (parked before this set) | -- | prior parking, unchanged. |
+| `qingyan_alpha.png` | 清言·AI生成 (parked before this set) | -- | prior parking, unchanged. |
+| `hailuo_alpha.png` | Hailuo AI image wordmark (parked before this set; the VIDEO label is registered) | -- | prior parking, unchanged. |
+| `catlogo_alpha.png` | outline cat-head + AI生成 (parked before this set) | -- | prior parking, unchanged. |