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/escalation-pending.txt

@@ -0,0 +1,42 @@
+# Skills whose escalation rule has not been written yet (#37).
+#
+# This list only shrinks. A skill here is exempt from the '## Escalation'
+# requirement until someone writes its real stop conditions; a skill that HAS a
+# section and is still listed fails the gate, so the list cannot outlive its
+# reason.
+#
+# The ones already done were the advisory and read-only skills, where the honest
+# answer is a line. What is left is the acting set — skills that write files,
+# dispatch agents, touch credentials or move releases — and each of those needs
+# a rule someone thought about, not a rote paragraph. Per #19, one at a time.
+
+atdd
+dream
+experiment-spec
+feature-spec
+gitea-ci
+own-the-task
+planning
+playwright
+problem-analysis
+refactoring
+regulatory-risk-assessment
+secret-hygiene
+session-retrospective
+spec-driven-dev
+superpowers-brainstorming
+superpowers-dispatching-parallel-agents
+superpowers-executing-plans
+superpowers-finishing-a-development-branch
+superpowers-receiving-code-review
+superpowers-requesting-code-review
+superpowers-subagent-driven-development
+superpowers-using-git-worktrees
+superpowers-using-superpowers
+superpowers-verification-before-completion
+superpowers-writing-plans
+superpowers-writing-skills
+tdd
+trainer
+user-stories
+web-shot