ci: verify the actions lockfile in CI

Fails the build when .github/workflows/actions.lock stops matching the
workflows, or when a locked pin no longer verifies upstream, so a stale or
tampered lockfile cannot go unnoticed between dependency updates.

.github/workflows/actions.lock

@@ -0,0 +1,32 @@
+# This file is machine-generated by `gh actions-lock`.
+# Do not edit by hand; run `gh actions-lock` to update.
+# Docs: https://gh.io/actions-lockfile
+version: 'v0.0.3'
+workflows:
+    '.github/workflows/ast-grep.yml': []
+    '.github/workflows/ci.yml': []
+    '.github/workflows/freebsd.yml': []
+    '.github/workflows/house-rules.yml': []
+    '.github/workflows/lockfile.yml':
+        - 'actions/checkout@v7.0.1'
+        - 'step-security/harden-runner@v2.22.4'
+    '.github/workflows/nix.yml':
+        - 'actions/checkout@v7.0.1'
+        - 'step-security/harden-runner@v2.22.4'
+    '.github/workflows/packaging-lint.yml':
+        - 'actions/checkout@v7.0.1'
+        - 'step-security/harden-runner@v2.22.4'
+    '.github/workflows/release.yml': []
+    '.github/workflows/sonarcloud.yml': []
+    '.github/workflows/windows-arm64.yml': []
+dependencies:
+    'actions/checkout@v7.0.1':
+        ref: 'v7.0.1'
+        commit: 'sha1-3d3c42e5aac5ba805825da76410c181273ba90b1'
+        owner_id: 44036562
+        repo_id: 197814629
+    'step-security/harden-runner@v2.22.4':
+        ref: 'v2.22.4'
+        commit: 'sha1-1d88384fd173af6ecb012dfd0264a306b711241a'
+        owner_id: 88700172
+        repo_id: 422287306

.github/workflows/lockfile.yml

@@ -0,0 +1,34 @@
+name: Lockfile
+
+# Fails when .github/workflows/actions.lock is out of sync with the workflows, or when a locked pin
+# no longer verifies upstream, so a moved tag cannot slip a different commit into a run.
+# Docs: https://gh.io/actions-lockfile
+on:
+  pull_request:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+env:
+  GH_TOKEN: ${{ github.token }}
+
+jobs:
+  lockfile:
+    name: Lockfile is in sync
+    runs-on: ubuntu-24.04
+    timeout-minutes: 10
+    steps:
+      - name: Harden runner
+        uses: step-security/harden-runner@v2.22.4
+        with:
+          egress-policy: audit
+      - uses: actions/checkout@v7.0.1
+        with:
+          persist-credentials: false
+      - name: Install gh-actions-lock
+        run: gh extension install github/gh-actions-lock --pin v0.4.1
+      - name: Verify the lockfile
+        run: gh actions-lock --verify

.github/workflows/nix.yml

@@ -28,10 +28,10 @@ jobs:
     timeout-minutes: 5
     steps:
       - name: Harden runner
-        uses: step-security/harden-runner@1d88384fd173af6ecb012dfd0264a306b711241a # v2.22.4
+        uses: step-security/harden-runner@v2.22.4
         with:
           egress-policy: audit
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: actions/checkout@v7.0.1
       - name: Git dependencies come from storytold
         run: |
           set -euo pipefail

.github/workflows/packaging-lint.yml

@@ -28,10 +28,10 @@ jobs:
     runs-on: windows-latest
     steps:
       - name: Harden runner
-        uses: step-security/harden-runner@1d88384fd173af6ecb012dfd0264a306b711241a # v2.22.4
+        uses: step-security/harden-runner@v2.22.4
         with:
           egress-policy: audit
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: actions/checkout@v7.0.1
         with:
           persist-credentials: false
       - name: Install the pinned packaging toolchain

sonar-project.properties

@@ -1,2 +1,11 @@
 sonar.projectKey=storytold_soundcraft
 sonar.organization=storytold
+
+# githubactions:S7637 asks for every action to be pinned to a commit SHA. A workflow covered by
+# .github/workflows/actions.lock runs the commit the lockfile records, so its tag refs are pinned
+# and the lockfile covers the actions those actions use too. Sonar does not read lockfiles yet, so
+# the rule flags the tag refs anyway:
+# https://community.sonarsource.com/t/githubactions-s7637-false-positives-for-actions-pinned-through-native-actions-lock/190814
+sonar.issue.ignore.multicriteria=gha-lockfile
+sonar.issue.ignore.multicriteria.gha-lockfile.ruleKey=githubactions:S7637
+sonar.issue.ignore.multicriteria.gha-lockfile.resourceKey=.github/workflows/**