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>

registry/formats.json

@@ -80,7 +80,15 @@
       "schema": "spot-check.schema.json",
       "status": "candidate",
       "chapter": "spec/08-fidelity.md",
-      "description": "The payload a spot-check key signs to seed a sample; never a file of its own."
+      "description": "The input a spot-check key proves a VRF output for, to seed a sample; never a file of its own."
+    },
+    {
+      "format": "scienting-proof/1",
+      "media_type": "application/vnd.scienting.proof+json",
+      "schema": "proof.schema.json",
+      "status": "candidate",
+      "chapter": "spec/08-fidelity.md",
+      "description": "An RFC 9162 inclusion proof for one item of a receipt, or a consistency proof between two revisions."
     },
     {
       "format": "scienting-rights/1",
@@ -233,6 +241,22 @@
       "status": "provisional",
       "chapter": "spec/08-fidelity.md",
       "description": "A check of an export against a named standard, covered by a receipt."
+    },
+    {
+      "format": "scienting-log-entry/1",
+      "media_type": null,
+      "schema": "log-entry.schema.json",
+      "status": "provisional",
+      "chapter": "spec/23-log.md",
+      "description": "One item of a team's transparency log: a receipt, revocation or roster by kind, ID and hash."
+    },
+    {
+      "format": "scienting-checkpoint/1",
+      "media_type": "text/plain; charset=utf-8",
+      "schema": "checkpoint.schema.json",
+      "status": "provisional",
+      "chapter": "spec/23-log.md",
+      "description": "A signed checkpoint of a team's log: a signed note with the origin, size and root."
     }
   ]
 }