contracts: Receipt v1 schema, canonicalization, verify rules, test vectors

test_vectors/README.md

@@ -0,0 +1,14 @@
+# Receipt v1 Test Vectors
+
+Each receipt JSON file is a full v1 envelope with `blake3` and `sha256` set to the
+expected canonical hashes.
+
+`manifest.json` repeats the expected canonical digests for convenience.
+Signature fields in `receipt_v1_signed.json` are placeholders and are not
+expected to verify unless explicitly noted in `manifest.json`.
+
+Canonical bytes are computed by:
+- removing hash and signature fields (`hash_alg`, `blake3`, `sha256`, `sig_alg`,
+  `signer_pub`, `signature`, `signed_at`)
+- recursively sorting object keys
+- serializing as compact UTF-8 JSON (no trailing newline)