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/invalid/signer-mismatch/package/MANIFEST.json

@@ -1 +1 @@
-{"doc":"scienting-doc/1","files":[{"path":"document.json","sha256":"20a7d6ba83bf42a87e44f3b3f96bfb16ff545b199d82e54d3c17989e465281df","size":555},{"path":"nodes.jsonl","sha256":"ffeffbf15cc9fe8182a31ef0bac32c1aef8c7a119706ac1e8a55aad218d0622c","size":11295},{"path":"provenance.json","sha256":"4bc7649bf6d3113f6c72b4016713654f57c8f03069632eabd1e6025c05cb9dac","size":226},{"path":"receipts.jsonl","sha256":"a95aa81bd99e2c5e1e6452b45ccf97b3ba50ff0a191fdb2050cedd7f8a0400e7","size":2181},{"path":"references.jsonl","sha256":"bb5445037c28bf5fde215b4b831c29327dec6dd88259e2d53aabb995f2fdb98f","size":60},{"path":"roster.json","sha256":"4a6d29e8968143a4e19f485741c513245df1de77eec4ef9b3047c71db45cda22","size":924},{"path":"witnesses.json","sha256":"83ac4411c2efe65e0f7fc4c9336abbef6977cd32b0f90de029a7f8516afc3e97","size":750}],"format":"scienting-package/1","key":"tiny2026example"}
+{"doc":"scienting-doc/1","files":[{"path":"document.json","sha256":"20b269257831ddd1d064586fcee2c4b21c96c0c660bd3b4d0996197724e4b4e7","size":742},{"path":"nodes.jsonl","sha256":"6ce54e0d837dceb4a2a39c1b2618cc66e16684b93f71b93ab4e6e709a90b0e52","size":11295},{"path":"provenance.json","sha256":"4bc7649bf6d3113f6c72b4016713654f57c8f03069632eabd1e6025c05cb9dac","size":226},{"path":"receipts.jsonl","sha256":"c2f0b12ef0543bff761960e4855d5eca95d97d70a992a3b2cb5f28a43f6133f6","size":2183},{"path":"references.jsonl","sha256":"59908a8aff6a2d5800747a1f45c6c2943ea1e31e7e1f10b6348967d30f16b87e","size":60},{"path":"roster.json","sha256":"4a6d29e8968143a4e19f485741c513245df1de77eec4ef9b3047c71db45cda22","size":924},{"path":"witnesses.json","sha256":"83ac4411c2efe65e0f7fc4c9336abbef6977cd32b0f90de029a7f8516afc3e97","size":750}],"format":"scienting-package/1","key":"tiny2026tiny-j4qm"}