feat: minted keys, VRF seeds, RFC 9162 proofs, history roots, tag URIs and a transparency log

Keys (spec/02 §2.4), the rule paperstack settled on:
- A work key is a Scholar-style citation key, a hyphen and the first four
  Crockford base32 characters of SHA-256("scienting-key/1:" + identity),
  where the identity is the first of doi, arxiv, isbn, pmid, pmcid and
  openalex in same_as, else the folded title, year and family name. A
  collision lengthens the later key by two characters; a key is minted
  once and never recomputed. A document key adds .si, .v<seq> or .<type>
  for versions other than the version of record.
- Every fixture key is now minted (hale2026harmonic-damb,
  okafor2025solvent-acth, writer2027fixed-ynr7.v3, tiny2026tiny-j4qm), so
  every node and record ID was re-minted and the docs rewritten to match.
  The validator checks the document key against the work key and version
  (doc.key.work) and the hash part against the identifier (doc.key.suffix).
  vectors/keys.jsonl pins the cases paperstack's tests pin.

Review:
- Spot-check seeds are ECVRF-EDWARDS25519-SHA512-TAI proofs (RFC 9381),
  implemented in tools/oracle/vrf.py in plain Python and reproduced
  against the RFC's Example 16; the sample ranks by the VRF output. The
  earlier Ed25519 seed could be ground by a dishonest checker.
- RFC 9162 inclusion and consistency proofs (crypto.inclusion_path,
  verify_inclusion, consistency_proof, verify_consistency) with
  scienting-proof/1, vectors/proofs.jsonl and two fixture records.
- document.json carries `history`, the root over the corrections, with
  the empty-tree hash for none (spec/11 §11.5, rule doc.history).
- A provisional transparency log (spec/23): log entries, signed-note
  checkpoints with key hashes as transparency logs share them, the rule
  that a logged revocation beats a self-asserted time, and vectors.
- Reserved signature schemes cose and ml-dsa-65 (spec/08 §8.4).

Identifiers and text:
- urn:scienting: becomes tag:scient.ing,2026: (RFC 4151), since the URN
  namespace was never registered.
- Unicode 16.0 is pinned for normalization and categories (spec/01 §1.4);
  the checker refuses another version.

Checking:
- check.py: keys, proofs, VRF and checkpoint vectors; the proof and
  checkpoint records; a check that every ID and hash the prose quotes
  exists in the fixtures or vectors; three more broken packages
  (history-wrong, key-suffix, key-work).
- stress.py: key, VRF, proof and checkpoint properties.
- Docs: a keys section in the concepts and FAQ, rationale entries for
  keys, VRF, proofs, tag URIs and the Unicode pin, a "Looking ahead"
  section, media-type registration and OCI distribution notes.

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

fixtures/records/anchor-keyed.json

@@ -1 +1 @@
-{"context":{"column_path_mac":["8de5d9cfdf71c50b161f357ab526bc7ffadd407c49c642a10112bb41cc4e1bc1","31824d3d0594c075074ff3a88e4c571e1f856218179a809f4f69bd5891ee7ff8"],"row_path_mac":["1db463578fc748d9686a5a1355c2a08086f4f331b546ec3273dd5e49ff1d178d","74bdccbc71693a4f8046f2e92bc477ff04fc5e04a8998e3ee189ba6b72b971e0"],"table_label_mac":"6943d614b69c7b2458c337ead13591262e932934151c27862ec0d47e4d560641"},"doc":"hale2026harmonic","format":"scienting-anchor/1","keyed":{"context":"layer:smithlab/kp4m2x7q","pages":["9dd865c7a19b44dc97a5d236859ed79174b25b72a5781d8df4f091d096de8908","1feb6882031349ca5eee822557bab0b6b0436a2d132ae8ca03babac2ff1948b8"],"scheme":"hkdf-pages"},"kind":"cell","node":"nkm3xn5","node_hash":"3cc6c2e26b027c5ed5b258c225daba349662315e3a0b3999346b61e580acdc4e","own_hash":"f7f3e9f91b3b20d5f9cd3e6704b22e5173f3464ddf2a78e7d8c80488e71a6443","quote":{"length":5,"mac":"0d8d4fcd55f1a4cfd7f254d597b7a5777b8865eb371283c03527ac8195ebb5ac"},"rev":12,"store":"smithlab"}
+{"context":{"column_path_mac":["8de5d9cfdf71c50b161f357ab526bc7ffadd407c49c642a10112bb41cc4e1bc1","31824d3d0594c075074ff3a88e4c571e1f856218179a809f4f69bd5891ee7ff8"],"row_path_mac":["1db463578fc748d9686a5a1355c2a08086f4f331b546ec3273dd5e49ff1d178d","74bdccbc71693a4f8046f2e92bc477ff04fc5e04a8998e3ee189ba6b72b971e0"],"table_label_mac":"6943d614b69c7b2458c337ead13591262e932934151c27862ec0d47e4d560641"},"doc":"hale2026harmonic-damb","format":"scienting-anchor/1","keyed":{"context":"layer:smithlab/kp4m2x7q","pages":["9dd865c7a19b44dc97a5d236859ed79174b25b72a5781d8df4f091d096de8908","1feb6882031349ca5eee822557bab0b6b0436a2d132ae8ca03babac2ff1948b8"],"scheme":"hkdf-pages"},"kind":"cell","node":"c20cna6","node_hash":"3efa98f63b493f7ba3ed01153859d3e0069fc39e1c51078b1239dedf0a4fc601","own_hash":"7bad196fc9634da03db3e418dfad50aa6b193acf9047e31db8908d9466c5ba40","quote":{"length":5,"mac":"0d8d4fcd55f1a4cfd7f254d597b7a5777b8865eb371283c03527ac8195ebb5ac"},"rev":12,"store":"smithlab"}