fix(ci): GitHub Actions security hardening

.github/dependabot.yml

@@ -0,0 +1,10 @@
+# See GitHub's documentation for more information on this file:
+# https://docs.github.com/en/code-security/supply-chain-security/keeping-your-dependencies-updated-automatically/configuration-options-for-dependency-updates
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    cooldown:
+      default-days: 3

.github/workflows/actionlint.yaml

@@ -7,11 +7,15 @@ on:
   pull_request:
     branches: [ 'main', 'release-*' ]
 
+permissions: {}
+
 jobs:
 
   action-lint:
     name: Action lint
     runs-on: ubuntu-latest
+    permissions:
+      contents: read   # actions/checkout + action-actionlint read the tree
 
     steps:
       - name: Harden Runner
@@ -21,6 +25,8 @@ jobs:
 
       - name: Check out code
         uses: actions/checkout@9bb56186c3b09b4f86b1c65136769dd318469633 # v4.1.2
+        with:
+          persist-credentials: false
 
       - name: Find yamls
         id: get_yamls

.github/zizmor.yml

@@ -0,0 +1,12 @@
+rules:
+  dependabot-cooldown:
+    config:
+      days: 3
+  # Cosmetic pedantic-only findings — suppressed per the campaign
+  # zizmor-config recipe. concurrency-limits fired against this repo's
+  # Action Lint workflow (docs.zizmor.sh/audits/#concurrency-limits);
+  # anonymous-definition is disabled as a standing campaign convention.
+  anonymous-definition:
+    disable: true
+  concurrency-limits:
+    disable: true