Run shellcheck in the local gate, at CI's exact pin

The gate checked ktlint, detekt and Android lint but not shellcheck, so a new or
edited .sh file was precisely the case where the hook passed and CI's Static
analysis leg still went red. The first file it could not check was itself, and it
was caught by hand twice before it was caught here.

THE DIGEST IS READ OUT OF status_check.yml RATHER THAN COPIED. shellcheck 0.9.0
and 0.11.0 disagree about how to report a trap handler -- SC2317 on seven body
lines against SC2329 once on the declaration, same script, same directive, one
red and one green. That is why CI pins by digest, and it is also why a second
copy of the digest in this file would be worse than none: when it drifts, the
symptom is the gate passing and CI failing, which is the exact failure this
section prevents.

Runs over `git ls-files '*.sh'` -- all tracked files, not the diff -- because
that is what CI does, and the job here is to predict that leg rather than audit
the change. podman is preferred over docker for the mount's SELinux relabel;
neither present, or the digest unreadable, reports the check as NOT COVERED
rather than skipping it quietly.

Verified that it bites rather than assumed: a probe script whose only fault was
an unquoted `ls $foo` was staged, and the real pre-commit hook blocked on SC2086
before it reached the JVM gate. Probe removed; all tracked .sh are clean under
the pinned digest.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tools/git-hooks/local-gate.sh

@@ -105,6 +105,50 @@ done <<< "$changed_files"
 
 # --- the cheap gate always runs -----------------------------------------------------------
 
+# --- shellcheck, at CI's exact pin ---------------------------------------------------------
+# WHY THIS IS HERE. The gate ran ktlint, detekt and Android lint but not shellcheck, so a new or
+# edited `.sh` file was precisely the case where this hook passed and CI's Static analysis leg
+# still went red. That is not hypothetical: this script is itself a new `.sh` file, and the first
+# thing it could not check was itself. It was caught by hand twice before it was caught here.
+#
+# THE DIGEST IS READ OUT OF status_check.yml, NOT COPIED INTO THIS FILE. shellcheck 0.9.0 and
+# 0.11.0 disagree about how to report a trap handler -- SC2317 on seven body lines versus SC2329
+# once on the declaration, same script, same directive, one red and one green. That disagreement
+# is why CI pins by digest, and a second copy of the digest here would drift from it silently.
+# When it drifts, the symptom is this gate passing and CI failing: the exact thing this section
+# exists to prevent. So there is one digest in the repo and this reads it.
+#
+# ALL TRACKED FILES, not just changed ones, because that is what CI does -- `git ls-files '*.sh'`.
+# The point is to predict that leg, not to audit the diff.
+shellcheck_pin="$(grep -oE 'koalaman/shellcheck@sha256:[0-9a-f]{64}' \
+  .github/workflows/status_check.yml | head -1)"
+runtime=""
+for candidate in podman docker; do
+  if command -v "$candidate" >/dev/null 2>&1; then
+    runtime="$candidate"
+    break
+  fi
+done
+
+if [ -z "$shellcheck_pin" ]; then
+  say "NOT COVERED: shellcheck. Could not read the pinned digest out of
+  .github/workflows/status_check.yml -- if that pin moved or was reformatted, fix this grep
+  rather than leaving the check silently absent."
+elif [ -z "$runtime" ]; then
+  say "NOT COVERED: shellcheck. Neither podman nor docker is on PATH, and there is no shellcheck
+  system package on this host. CI's Static analysis leg is what answers for .sh files then."
+else
+  # :z is podman's SELinux relabel and is what this host needs; docker on CI does without it.
+  mount=":z"
+  [ "$runtime" = "docker" ] && mount=""
+  say "shellcheck ($runtime, $shellcheck_pin)"
+  if ! git ls-files -z '*.sh' |
+    xargs -0 -r "$runtime" run --rm -v "$PWD:/mnt$mount" "docker.io/$shellcheck_pin"; then
+    die "shellcheck failed. CI runs the same digest over the same files, so this is a red
+  Static analysis leg waiting to happen."
+  fi
+fi
+
 say "$MODE: running the JVM gate"
 if ! ./gradlew "${GRADLE_GATE[@]}" --continue; then
   die "the JVM gate failed (assemble, unit tests, androidTest compile, ktlint, detekt, lint)."