fix(checkpoints): GW-17 could never have run

The checkpoint runner rejects the pattern GW-17 shipped with. Measured by
sourcing is_safe_eval_command out of automated-assessment's
run-checkpoints.sh and calling it:

  OLD: REJECTED — pattern contains command-chaining metacharacter (; && || ` $())
  NEW: accepted

Two independent reasons, both fatal: the allowlist rejects `$(`, `;`,
`&&`, `||` and backticks outright, and a multi-line YAML scalar reaches
the runner as an EMPTY pattern ("checkpoint likely uses multi-line YAML
scalar; use single-line pattern"). A mechanical checkpoint that cannot
execute is the same defect this branch exists to remove, one layer up.

GW-17 is now single-line, HEAD-only, and free of chaining
metacharacters. `sed -n -e '/^$/q' -e p` is the semicolon-free spelling
of the header cut, so the message-body false positive stays closed —
verified against a commit whose body starts with `gpgsig`. The sweep over
several commits stays where a full shell is available:
verify-git-workflow.sh (last 10) and signing-preflight.sh. Mirroring
rather than reproducing is the arrangement skill-repo already documents
for SR-37.

The suite now asserts both allowlist constraints on the pattern, so the
next edit cannot reintroduce either.

Signed-off-by: Sebastian Mendel <github@sebastianmendel.de>

Author: CybotTM

skills/git-workflow/checkpoints.yaml

@@ -151,12 +151,20 @@ mechanical:
   # unsigned, which fails a fully signed repository. Whether a signature
   # verifies is the host's answer (GW-11 / the commits API), not this one's.
   # Kept in step with signing-preflight.sh by tests/test_signing_preflight.sh.
+  #
+  # HEAD only, single line, and no `$(`/`;`/`&&`: the checkpoint runner's
+  # allowlist (is_safe_eval_command in automated-assessment's
+  # run-checkpoints.sh) rejects command-chaining metacharacters outright, and a
+  # multi-line YAML scalar reaches it as an EMPTY pattern. A loop over the last
+  # five commits satisfies neither, so this mirrors the rule rather than
+  # reproducing it — the same arrangement as SR-37 in skill-repo. The full
+  # sweep lives in verify-git-workflow.sh (last 10) and signing-preflight.sh.
+  # `sed -n -e '/^$/q' -e p` is the semicolon-free spelling of the header cut.
   - id: GW-17
     type: command
-    pattern: |-
-      test -z "$(git log -5 --format=%H | while read -r c; do git cat-file commit "$c" | sed -n '/^$/q;p' | grep -qE '^gpgsig(-sha256)? ' || echo "$c"; done)"
+    pattern: "git cat-file commit HEAD | sed -n -e '/^$/q' -e p | grep -qE '^gpgsig(-sha256)? '"
     severity: info
-    desc: "Recent commits should carry a GPG/SSH signature"
+    desc: "HEAD should carry a GPG/SSH signature"
 
 llm_reviews:
   # === CONVENTIONAL COMMITS ===

tests/test_signing_preflight.sh

@@ -174,7 +174,15 @@ CHECKPOINTS="$REPO_ROOT/skills/git-workflow/checkpoints.yaml"
 
 # Extracted with awk rather than a YAML parser: CI installs no PyYAML, and a
 # test that needs a dependency the runner lacks is a test that does not run.
-gw17=$(awk '/^  - id: GW-17$/{f=1} f && /^      test -z/{print; exit}' "$CHECKPOINTS")
+gw17=$(awk '/^  - id: GW-17$/{f=1} f && /^    pattern: /{sub(/^    pattern: "/, ""); sub(/"$/, ""); print; exit}' "$CHECKPOINTS")
+
+# The checkpoint runner's allowlist (is_safe_eval_command) rejects `$(`, `;`,
+# `&&`, `||` and backticks outright, and a multi-line YAML scalar reaches it as
+# an empty pattern. A checkpoint that trips either never runs — the exact
+# failure this whole branch is about, one layer up.
+check "GW-17's pattern is a single line" 1 "$(wc -l <<<"$gw17")"
+check "GW-17's pattern has no chaining metacharacters" 0 \
+    "$(grep -cE '[;`]|&&|\|\||\$\(' <<<"$gw17")"
 
 # The load-bearing part is the header pattern. Every place that answers "is this
 # commit signed" must use the same rule, or one of them silently becomes a