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/layer/receipt.json

@@ -1 +1 @@
-{"at":"2026-10-11T19:30:00Z","by":"ana","doc":"hale2026harmonic","evidence":[],"format":"scienting-receipt/1","id":"pgtc2enctchze","level":"F3","nodes":[],"records":[["annotation","c9herrt41fcpr","4c25a14e30ef552a5993aeed3a818db3f67bb5e6422ce27c110862d485664fbd"],["annotation","jgk1n6dcvwbvw","2bc845ce83be9f19580310fbc974fc4b916ea75933996096c7bb72d5c76a44cb"],["annotation","shn6geqn0rhvs","9af1f3a2d2a97ce871337d87a397746b3010a2391917053deb3162e7533baf01"],["annotation","tj573y8mhap0f","0e70a9b6a05e16dc6c55ac27c963ae1820d39387521dd2ee1d0e77be683b85a5"],["annotation","v5pk0zcbsxa4b","78873fd145b89faa9bcda800fce9d0f5a057ce10fc0f94d95141d3d9fba85636"]],"rev":12,"root":"1d172f9491c225044a3b9bf42c2c4524a24e587562fa455941d80221b425d02e","scope":"targeted:layer","signature":{"key":"ana","scheme":"ed25519","value":"fEH0tDCkbVeRsjBgKS+ZphoZYaltQ0l53XgWrH/aWCOnl0P4diRFzcj1rheqW7Tck+gSmlLl0xtLmYDtjCPaAw=="}}
+{"at":"2026-10-11T19:30:00Z","by":"ana","doc":"hale2026harmonic-damb","evidence":[],"format":"scienting-receipt/1","id":"r10e5mzvw6tja","level":"F3","nodes":[],"records":[["annotation","f4s8pc1hdhd9d","9db553d2150a912e4ba3027d002706e08ccaded843d3e49c79b95a2e0581b6f1"],["annotation","gb5tmv3hq08vz","3b776d37af21d1bdfd3a0130c9bfa26affa484fb4d76e41d83cbd8bb02b4975c"],["annotation","nzwtq23khdx4s","8ea94b7a3d266f51e11dd31399784019acd1b1b53ed093e15c199417327992ab"],["annotation","whcypxav2cqbx","11845db3ef685b0b9bd13895cc5b8ade5b345ee7d72737a630be60d690a2ba5d"],["annotation","y7bd3he0jwjbx","0286ede04d8bf548432e34dd7beeee0fb044bd43022a8661a292018dd2ef5578"]],"rev":12,"root":"246581b0926273458b78ece15b465f0567c150a1e071f72322ce41895f9502e1","scope":"targeted:layer","signature":{"key":"ana","scheme":"ed25519","value":"WMDdARYwB0ETltF57ks1MxJ6ny/c4XziLvYUBd8PoW7MwcfhPKmDTqNGxRNg4z5g4c/bHnWS4ftZLJiONTL/Cg=="}}