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>

docs/overview.md

@@ -26,7 +26,7 @@ The formats supply those three, and they are worth most at the scale of one team
 
 paperspec is a set of file formats for scientific papers that have been converted, split into addressable pieces and checked.
 The repository is at <https://git.scient.ing/infra/paperspec>.
-It is version 0.1.0 and defines 29 formats; in [registry/formats.json](../registry/formats.json), 18 are `candidate` and 11 are `provisional`.
+It is version 0.1.0 and defines 32 formats; in [registry/formats.json](../registry/formats.json), 19 are `candidate` and 13 are `provisional`.
 
 ## Who it is for
 
@@ -51,12 +51,12 @@ It appears inside hashed data and test vectors, and it is separate from the repo
 
 | Folder | Holds |
 | --- | --- |
-| [spec/](../spec/README.md) | The specification, in 23 chapters (00 to 22). Normative. |
-| [schemas/](../schemas/README.md) | 39 JSON (plain-text data format) Schemas for the files and records. |
+| [spec/](../spec/README.md) | The specification, in 24 chapters (00 to 23). Normative. |
+| [schemas/](../schemas/README.md) | 42 JSON (plain-text data format) Schemas for the files and records. |
 | [registry/](../registry/README.md) | The list of formats, the rule IDs a checker reports, download-stamp rules, and default rights requirements. |
 | [tools/](../tools/README.md) | Reference programs: `check.py` checks everything, `build.py` rebuilds the fixtures and vectors, `load.py` loads packages into SQLite, and `oracle/` is a compact implementation of every rule. |
-| [vectors/](../vectors/README.md) | 21 files of test vectors: inputs and the exact outputs every implementation must compute. |
-| [fixtures/](../fixtures/README.md) | Five valid example packages, one of them also as a zip, 28 deliberately broken ones that each break one named rule, example records, and the test keys that signed them. All text is synthetic. |
+| [vectors/](../vectors/README.md) | 25 files of test vectors: inputs and the exact outputs every implementation must compute. |
+| [fixtures/](../fixtures/README.md) | Five valid example packages, one of them also as a zip, 31 deliberately broken ones that each break one named rule, example records, and the test keys that signed them. All text is synthetic. |
 | [sql/](../sql/README.md) | Tables for SQLite, Dolt and PostgreSQL, and a SQLite bundle with full-text search. |
 | [context/](../context/README.md) | The JSON-LD context that makes annotation layers W3C Web Annotations. |
 | [docs/](README.md) | Guides, including this page. |
@@ -107,7 +107,7 @@ The [specification's reading paths](../spec/README.md) say which chapters each r
    A store loads the package into a database.
    A reader renders it with layers of annotations.
    Anchors (stored references to a sentence, with its hash and a quotation) let a claim, a dataset value or a draft's citation point at a passage.
-   Datasets, drafts, views, projects, exercises and checklists are `provisional` formats.
+   Datasets, drafts, views, projects, exercises, checklists and the transparency log are `provisional` formats.
 7.
    Check and sign.
    People proofread what matters and sign receipts; second reviewers spot-check them.