feat: ML-DSA-65, did:key, named hash algorithm, model provenance, log tiles and witnesses

- hashing.algorithm names the hash function in every document; a consumer refuses one it does not implement (doc.hash.algorithm)
- ML-DSA-65 (FIPS 204) is an implemented signature scheme: pure-Python reference in tools/oracle/mldsa.py checked against NIST ACVP vectors, a receipt signed by the new roster key dana, and signature vectors for key generation and a deterministic signature
- roster keys may carry a did:key, which the validator checks against the public key (doc.roster.did), and a witness purpose for parties that cosign log checkpoints
- model provenance: a correction's author and an annotation's generator name the model with provider, version and the hashes of its weights, prompt and parameters, and where it ran
- the transparency log gains the tlog-tiles static layout (fixtures/records/log/), a project settings.log with origin, witnesses and threshold, and an acceptance rule; the fixture checkpoint is cosigned by a witness
- store.sql: roster_keys accepts cose and ml-dsa-65 and gains a did column
- spec chapters 01, 08, 11, 18, 20 and 23, the rationale, glossary, fixture, vector and tool guides updated; stress harness covers ML-DSA

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tools/oracle/receipts.py

@@ -10,7 +10,7 @@ import math
 from fractions import Fraction
 from math import comb
 
-from . import crypto, jcs, vrf
+from . import crypto, jcs, mldsa, vrf
 from .model import LEVELS
 from .text import record_id, sha256_hex
 
@@ -48,20 +48,38 @@ def _b64(s):
 
 
 def verify_signature(rec, roster):
-    """Whether the record's Ed25519 signature verifies under the roster key it names. Never raises."""
+    """Whether the record's signature verifies under the roster key it names, for the schemes the tools implement
+    (`ed25519` and `ml-dsa-65`); any other scheme does not verify. Never raises."""
     sig = rec.get("signature") or {}
     if not isinstance(sig, dict):
         return False
     key = roster.get(sig.get("key"))
-    if not key or sig.get("scheme") != "ed25519" or key.get("scheme") != "ed25519":
+    if not key or sig.get("scheme") != key.get("scheme"):
         return False
     pub, value = _b64(key.get("public", "")), _b64(sig.get("value", ""))
-    if pub is None or value is None or len(pub) != 32 or len(value) != 64:
+    if pub is None or value is None:
         return False
     try:
-        return crypto.ed25519_verify(pub, signing_payload(rec), value)
+        if sig["scheme"] == "ed25519":
+            return len(pub) == 32 and len(value) == 64 and crypto.ed25519_verify(pub, signing_payload(rec), value)
+        if sig["scheme"] == "ml-dsa-65":
+            return mldsa.verify(pub, signing_payload(rec), value)
     except (ValueError, TypeError):
         return False
+    return False
+
+
+def seal_mldsa(rec, sk, key_id):
+    """Fill in a record's root (for receipts), ID and ML-DSA-65 signature, deterministically."""
+    rec = dict(rec)
+    if rec["format"] == "scienting-receipt/1":
+        rec["root"] = crypto.merkle_root(crypto.receipt_items(rec))
+    rec.pop("id", None)
+    rec.pop("signature", None)
+    sig = mldsa.sign(sk, signing_payload(rec))
+    rec["id"] = record_id(record_hash(rec))
+    rec["signature"] = {"scheme": "ml-dsa-65", "key": key_id, "value": base64.b64encode(sig).decode("ascii")}
+    return rec
 
 
 def key_valid_at(key, at):