feat(check): every skill states when it stops and hands back

Implements #5's decision. The hard part was #37's, not #5's: which skills need
an escalation rule? A hardcoded list rots, sniffing the prose for "does this
write anything" is unfalsifiable, and a frontmatter flag is the option #5
rejected wearing a hat.

So there is no acting set. Every skill answers the question, and a read-only one
answers it in a line. That turns an absence into a claim someone can disagree
with, which is the whole point — "this skill never hands back" is a design
decision worth stating, and today it was indistinguishable from nobody having
thought about it.

Eleven written here, all advisory or read-only, where the honest answer is short
and the value is in being specific rather than generic. `cognitive-load` stops
when the metric disagrees with the people reading the code, because that is
evidence about the metric. `test-design` stops when the tests are fine and the
design under test is what makes them awkward. `code-review` stops when the diff
is big enough that a review would be a skim, and says so rather than producing
confident coverage of a fraction.

The remaining thirty are the acting set — writes, dispatches, credentials,
releases — and each needs a rule someone thought about rather than a rote
paragraph, so they sit in bin/escalation-pending.txt. That list only shrinks,
and it is self-cleaning: a listed skill that HAS a section fails the gate, so an
exemption cannot outlive its reason. Mutation-verified both ways.

Six test cases including the stale-entry case, because an exemption for a skill
that no longer exists is how a gate quietly stops covering something.

Refs #37, closes the mechanism half
Bump-Type: minor

bin/check-escalation

@@ -0,0 +1,64 @@
+#!/bin/sh
+# check-escalation — every skill states when it stops and hands back.
+#
+# #5 decided this belongs in the body, not the frontmatter: no harness reads
+# frontmatter beyond name/description, so a `failure_criteria:` key would be a
+# guarantee nothing honours. The model reads the body.
+#
+# #37 then had to define which skills need one, and every obvious answer was
+# bad: a hardcoded list rots, sniffing the text for "does it write anything" is
+# unfalsifiable, and a frontmatter flag is the rejected option wearing a hat.
+#
+# So there is no acting set. EVERY skill answers the question. A read-only skill
+# answers it in one line — "read-only; findings are the output, nothing is
+# handed back" — which turns an absence into a claim someone can disagree with.
+#
+# bin/escalation-pending.txt is a ratchet for skills whose real rule has not
+# been written yet (a stop condition nobody thought about is not worth
+# enforcing). It is self-cleaning: a listed skill that HAS a section fails, so
+# the list cannot outlive its reason.
+#
+# Usage: check-escalation [checkout-root]
+
+set -u
+
+ROOT=${1:-$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)}
+PENDING="$ROOT/bin/escalation-pending.txt"
+fail=0
+
+listed() {
+  [ -f "$PENDING" ] || return 1
+  sed 's/#.*//' "$PENDING" | grep -qx "[[:space:]]*$1[[:space:]]*"
+}
+
+for dir in "$ROOT"/skills/*/; do
+  [ -f "$dir/SKILL.md" ] || continue
+  name=$(basename "$dir")
+
+  if grep -q '^## Escalation' "$dir/SKILL.md"; then
+    if listed "$name"; then
+      echo "ERROR: skills/$name has an Escalation section but is still in bin/escalation-pending.txt — remove it from the list" >&2
+      fail=1
+    fi
+    continue
+  fi
+
+  listed "$name" && continue
+  echo "ERROR: skills/$name has no '## Escalation' section — say when it stops and hands back, or say it never does" >&2
+  fail=1
+done
+
+# A pending entry for a skill that no longer exists is a stale exemption, and a
+# stale exemption is how a gate quietly stops covering something. Looped without
+# a pipe on purpose: a `while read` on the right of a pipe runs in a subshell,
+# so `fail=1` would be set in a process that exits before it is read.
+if [ -f "$PENDING" ]; then
+  entries=$(sed 's/#.*//' "$PENDING" | tr -d '[:blank:]' | grep -v '^$' || true)
+  for entry in $entries; do
+    [ -f "$ROOT/skills/$entry/SKILL.md" ] && continue
+    echo "ERROR: bin/escalation-pending.txt lists '$entry', which has no skills/$entry/SKILL.md" >&2
+    fail=1
+  done
+fi
+
+exit $fail