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/digitization-confirmation.json

@@ -1 +1 @@
-{"at":"2026-10-11T20:00:00Z","by":"ana","doc":"hale2026harmonic","evidence":[{"kind":"crop","node":"b2wgyq2","sha256":"41859f0385275a8386eef230d92fc34a379549dd475f27396dc6e8a94ca0fc54"}],"format":"scienting-receipt/1","id":"zkebjgvzja0x1","level":"F3","nodes":[],"records":[["digitization","qrqsy3x6bznxw","9892eb87d908f81475fab42150e0bd84dbfbf0b2cbfe399fbcb39458791cac92"]],"rev":12,"root":"08849d6580a6c8eeec5d10026b2dbdf9ed64a40fe03cfe16849f846fbf49fabb","scope":"targeted:digitization","signature":{"key":"ana","scheme":"ed25519","value":"tzrVLqyutIThRlraYBE8+FQR7gAOupeOFaN++lV6DhY6akEy8aeaU/mzU2U4yJhOLN8NFqXLVM3EsUc0ucf6BA=="}}
+{"at":"2026-10-11T20:00:00Z","by":"ana","doc":"hale2026harmonic-damb","evidence":[{"kind":"crop","node":"rzxn46v","sha256":"41859f0385275a8386eef230d92fc34a379549dd475f27396dc6e8a94ca0fc54"}],"format":"scienting-receipt/1","id":"s91x847fmg0gg","level":"F3","nodes":[],"records":[["digitization","n43jx89tgmmzy","b49029057a26af378a97fc1e740801f767934e49161e867ec552700e8eff75bc"]],"rev":12,"root":"8ec8914c43871ac949b14221bb71a145e484f80d6c169ec639efedffc3ed7979","scope":"targeted:digitization","signature":{"key":"ana","scheme":"ed25519","value":"2Gdqmv/PzL7j21NxSHprM8PgJtFQxI6L+pNkjV53RfMNJjEHRZfOnB9nVOzDfCJnGWuTvCS8+T9Qg6WapF60AQ=="}}