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>

tools/oracle/grade.py

@@ -3,18 +3,21 @@
 Non-normative; see spec/19-exercises.md.
 """
 
+from decimal import Decimal
 from fractions import Fraction
 
 from . import anchors as A
 from .tree import Refusal
 
 
-def dec(fr):
-    fr = Fraction(fr)
-    if fr.denominator == 1:
-        return str(fr.numerator)
-    s = "%.4f" % float(fr)
-    return s.rstrip("0").rstrip(".")
+def dec(d):
+    """A decimal string, exactly as the sum came out (spec/19 §19.4: points are decimal strings, summed exactly)."""
+    return format(Decimal(d), "f")
+
+
+def _zero_like(d):
+    """Zero with the scale of `d`, so a missed element worth "0.5" scores "0.0"."""
+    return Decimal(0).quantize(Decimal(d))
 
 
 def _resolved(state, anchor):
@@ -57,34 +60,34 @@ def grade(body, submission, state):
     items = []
 
     def item(name, pts, got, fb):
-        items.append({"element": name, "points": dec(pts if got else 0), "max": dec(pts), "feedback": fb})
+        items.append({"element": name, "points": dec(pts if got else _zero_like(pts)), "max": dec(pts), "feedback": fb})
 
     if kind in ("anchor", "check"):
         if kind == "check":
             v = key["verdict"]
             ok = ans.get("verdict") == v["value"]
-            item("verdict", Fraction(v["points"]), ok, v.get("feedback", {}).get("hit" if ok else "miss", ""))
+            item("verdict", v["points"], ok, v.get("feedback", {}).get("hit" if ok else "miss", ""))
         for i, el in enumerate(key["elements"]):
             ok = _any(state, rule, ans.get("anchors", []), el["anchors"])
-            item("element:%d" % i, Fraction(el["points"]), ok, el.get("feedback", {}).get("hit" if ok else "miss", ""))
+            item("element:%d" % i, el["points"], ok, el.get("feedback", {}).get("hit" if ok else "miss", ""))
     elif kind == "trace":
         chain = ans.get("chain", [])
         for i, link in enumerate(key["chain"]):
             ok = i < len(chain) and _any(state, rule, chain[i], link["anchors"])
-            item("link:%d" % i, Fraction(link["points"]), ok, link.get("feedback", {}).get("hit" if ok else "miss", ""))
+            item("link:%d" % i, link["points"], ok, link.get("feedback", {}).get("hit" if ok else "miss", ""))
     elif kind == "reproduce":
-        ok = abs(Fraction(ans["value"]) - Fraction(key["value"])) <= Fraction(key["tolerance"])
-        item("value", Fraction(key["points"]), ok, key.get("feedback", {}).get("hit" if ok else "miss", ""))
+        ok = abs(Decimal(ans["value"]) - Decimal(key["value"])) <= Decimal(key["tolerance"])
+        item("value", key["points"], ok, key.get("feedback", {}).get("hit" if ok else "miss", ""))
     elif kind == "verify":
         flags = ans.get("flags", [])
         for i, err in enumerate(key["errors"]):
             hit = [f for f in flags if _any(state, rule, [f["anchor"]], err["anchors"])]
             ok = any(f["verdict"] == err["verdict"] for f in hit)
             fb = err.get("feedback", {}).get("hit" if ok else "miss", "")
-            item("error:%d" % i, Fraction(err["points"]), ok, fb)
+            item("error:%d" % i, err["points"], ok, fb)
     else:
         raise Refusal("grade.kind", "unknown exercise kind " + kind)
-    score = sum(Fraction(x["points"]) for x in items)
-    total = sum(Fraction(x["max"]) for x in items)
+    score = sum((Decimal(x["points"]) for x in items), Decimal(0))
+    total = sum((Decimal(x["max"]) for x in items), Decimal(0))
     return {"format": "scienting-grade/1", "submission": submission["id"], "exercise": submission["exercise"],
             "score": dec(score), "max": dec(total), "items": items}