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>

context/README.md

@@ -33,7 +33,7 @@ The repository's name, paperspec, is a separate matter.
 
 ## An example from the fixtures
 
-[`fixtures/records/layer/annotations.jsonl`](../fixtures/records/layer/annotations.jsonl) holds nine annotations on the example paper `hale2026harmonic`.
+[`fixtures/records/layer/annotations.jsonl`](../fixtures/records/layer/annotations.jsonl) holds nine annotations on the example paper `hale2026harmonic-damb`.
 The first is a `gloss`, an explanation for a novice, of the phrase "bond force constant".
 Shortened, it reads:
 
@@ -43,10 +43,10 @@ Shortened, it reads:
  "body": {"type": "TextualBody", "kind": "gloss", "audience": "novice",
           "value": "A *harmonic* term treats a bond like a spring: ..."},
  "target": {"type": "SpecificResource",
-            "source": "urn:scienting:doc:smithlab/hale2026harmonic",
+            "source": "tag:scient.ing,2026:doc:smithlab/hale2026harmonic-damb",
             "selector": [
               {"type": "AnchorSelector",
-               "anchor": {"format": "scienting-anchor/1", "node": "sxgcc9h",
+               "anchor": {"format": "scienting-anchor/1", "node": "rr20tev",
                           "span": [111, 130], "quote": {"exact": "bond force constant", "...": "..."}, "...": "..."}},
               {"type": "TextQuoteSelector", "exact": "bond force constant",
                "prefix": "rm{eq}})^2$$ where $K_r$ is the ", "suffix": " and $r_\\mathrm{eq}$ the equilib"}]}}
@@ -94,7 +94,7 @@ Three of the nine fixture annotations have only an `AnchorSelector` (the section
 
 - Writer: Put both URLs (web addresses), in the order shown, in `@context` of `layer.json` and of every line of `annotations.jsonl`. [Chapter 18](../spec/18-layers.md) defines layers (§18.2), annotations (§18.3) and bodies (§18.4).
 - Reader: Follow [chapter 6](../spec/06-anchors.md) to resolve an anchor.
-  The file `vectors/resolve.jsonl` resolves seventeen anchors against `fixtures/packages/hale2026harmonic` and gives every outcome.
+  The file `vectors/resolve.jsonl` resolves seventeen anchors against `fixtures/packages/hale2026harmonic-damb` and gives every outcome.
 - JSON-LD processor: Use a JSON-LD 1.1 processor; the context relies on `@json` and `@version` 1.1.
 - Checker: `schemas/annotation.schema.json` and `schemas/layer.schema.json` validate the files. `tools/check.py` also checks that each annotation's ID derives from its content and that the receipt at `fixtures/records/layer/receipt.json` covers each `confirmed` annotation.