Move the receipt gate to the model side

The gate head is fitted on the freeze CLIP-L-ft embedding space, so it
belongs with the model: _load_receipt_gate now prefers
receipt-gate-2026-09-02.npz from the Hub snapshot or the
RAIW_CLASSIFY_WEIGHTS directory, with the package asset kept as the
fallback for weights frozen before the gate existed. Card mode of the
publish workflow now uploads the gate alongside the README and the
operating point, and the snapshot allow-pattern includes it.

.github/workflows/publish-photo-classify-hf.yml

@@ -16,7 +16,7 @@ on:
         description: "Type publish"
         required: true
       mode:
-        description: "full = card plus weights from the release tag; card = README and operating-point only"
+        description: "full = card plus weights from the release tag; card = README, operating-point, and receipt gate only"
         type: choice
         options:
           - full