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>

CHANGELOG.md

@@ -15,7 +15,7 @@ The first release.
 - Work keys minted from a Scholar-style citation key and a hash of the work's identity, with document keys for versions; `tag:` URIs for layers, annotations and documents.
 - Spot-check seeds as VRF proofs (RFC 9381), RFC 9162 inclusion and consistency proofs, a history root over every document's corrections, and a provisional transparency log with signed checkpoints.
 - Signed QA reports, a conformance checklist covered by a receipt, and a `description` annotation for the figure descriptions an accessible export needs.
-- Reserved signature schemes for COSE and ML-DSA-65, and the character data pinned to Unicode 16.0.
+- ML-DSA-65 (FIPS 204) as a signature scheme, with a reference implementation checked against NIST's vectors; `cose` reserved; `did:key` identifiers for roster keys; the hash algorithm named in every document; model provenance by weights, prompt and parameters; witnesses and a static tile layout for the log; and the character data pinned to Unicode 16.0.
 - Guides for newcomers: an overview, the concepts, a walkthrough of the example paper, runnable examples, the rationale, a FAQ and a glossary.
 - Tools that build and check everything, validate packages and zipped packages and run proposed corrections through the gate, load packages into SQLite or a bundle, and stress the reference implementation with random inputs.
 - A pixi workspace pinned to Python 3.14, with tasks for checking, building, linting, validating and loading.