feat: zipped packages, target set, checklists, audit fixes and a stress test

Features for the next six months (accessible HTML export, paperpack and
Lode on packages, the personal bundle):

- Zipped packages: the oracle writes and reads `.sct.zip` archives under
  the rules of spec/12 §12.2; validate.py and load.py accept them; a
  byte-identical zip of the tiny package joins the fixtures, and two
  broken archives (traversal, symbolic link) join fixtures/invalid.
- The target set of targeted F3 (spec/08 §8.10) is computed by the
  oracle and pinned by vectors/targets.jsonl under each digit rule; the
  rule now covers cells as well as sentences and the leaves of anchored
  containers, and defines a node's section.
- scienting-checklist/1 (provisional): a conformance check of an export,
  covered by a receipt as ["checklist", id, hash] (spec/08 §8.11), with a
  WCAG 2.1 AA fixture and its receipt.
- QA reports are signed like receipts (spec/08 §8.9).
- A `description` annotation body with role alt or long, so an
  accessible export can find a confirmed figure description; the layer
  fixture carries one, and the store's body-kind constraint allows it.
- scienting-spot-check/1, the seed payload, is registered with a schema.
- exercise, submission and grade are provisional until a course has
  used them.

Audit fixes, each with a vector or a broken package where one was
missing:

- Folder packages: symbolic links are refused on validate and load,
  manifest paths must not collide under case folding, listed files are
  matched by exact name, files are hashed in chunks under a size limit.
- Files are compared byte for byte, so CR LF, a byte order mark, NaN,
  a lone surrogate or invalid UTF-8 is refused instead of translated;
  integers beyond 2^53 are read as doubles, as canonical JSON writes them.
- Receipts: signature.key must equal by and the key must be valid when
  signed; a qa receipt's nodes must be the sample at the original's
  hashes, its scope must name qa.of, its errors must be sampled nodes;
  statuses are computed once, iteratively, so chains of spot-checks
  hundreds deep settle; Base64 and manifest shape errors become refusals
  instead of tracebacks; counts and the fidelity of roster-less packages
  are recomputed.
- The gate enforces rule 11 of spec/11 §11.4: changed nodes are
  validated against the node schema and the references between nodes
  are checked, so a set to a bad value, an insert with unknown
  properties or a delete of a referenced header cell is refused; a
  relabel to null drops the label; a reclassify drops foreign
  attributes; a split strips whitespace across runs; ids.jsonl order
  follows spec/04 §4.4 in every state; a move after itself is refused.
- Anchors: the relabel rule requires that nothing else changed below the
  node; an alias chain ending in a deletion no longer crashes resolve.
- Notation: a script after an empty group applies to the previous atom
  ({}^{14}C); letters are defined by Unicode block in spec/05 §5.4 and
  the oracle; \left) is complex.
- Page fingerprints delete whitespace before folding, so "10 -20" and
  "10-20" fold alike (spec/07 §7.1).
- Grades are summed with exact decimals; the reviewer error bound is
  computed with integer arithmetic.
- receipts and revocations are keyed by (doc_key, id) in SQL, since one
  revocation may be carried by several packages.

Checking:

- tools/stress.py: seeded randomized property tests over canonical JSON,
  normalization, notation, random correction walks, anchor resolution,
  Merkle roots, spot-check samples, error bounds, fingerprints, mutated
  archives and packages, rights and spot-check chains; CI runs it.
- check.py verifies every count and version the prose states against
  the repository, the zipped fixture and crafted archives, the checklist
  coverage, and nine more broken packages.
- CONTRIBUTING.md gains a release checklist.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

registry/rules.json

@@ -198,6 +198,16 @@
       "description": "A node of a kind that takes no label has one.",
       "chapter": "spec/22-conformance.md"
     },
+    {
+      "id": "doc.node.schema",
+      "description": "A node a correction produced does not validate against the node schema (a property the kind does not take, or a bad shape).",
+      "chapter": "spec/11-corrections.md"
+    },
+    {
+      "id": "doc.counts",
+      "description": "document.json's counts are not the number of nodes and of leaves.",
+      "chapter": "spec/22-conformance.md"
+    },
     {
       "id": "doc.order.ids",
       "description": "ids.jsonl is not aliases by ID, then retirements by revision and ID.",
@@ -435,13 +445,28 @@
     },
     {
       "id": "package.path.unsafe",
-      "description": "A path is absolute, has an empty, `.` or `..` segment, a backslash or a NUL, or is not normalized.",
+      "description": "A path is absolute, has an empty, `.` or `..` segment, a backslash or a NUL, is not normalized, or is or passes through a symbolic link.",
       "chapter": "spec/22-conformance.md"
     },
+    {
+      "id": "package.size",
+      "description": "The package's files exceed the consumer's size limit.",
+      "chapter": "spec/12-package.md"
+    },
     {
       "id": "package.schema",
       "description": "A file or line does not validate against its schema.",
       "chapter": "spec/22-conformance.md"
+    },
+    {
+      "id": "package.zip.entry",
+      "description": "A zipped package is not a zip archive, or an entry is encrypted, a symbolic link, neither stored nor deflated, not marked as UTF-8, duplicated, unsafe as a path, or not under one top-level folder named by the key.",
+      "chapter": "spec/12-package.md"
+    },
+    {
+      "id": "package.zip.size",
+      "description": "A zipped package expands past the consumer's limit, or an entry holds more than its header declares.",
+      "chapter": "spec/12-package.md"
     }
   ]
 }