ci: add zizmor workflow + config (hash-pin policy)

Author: nicktrn

.github/workflows/zizmor.yml

@@ -0,0 +1,37 @@
+name: Zizmor
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - '.github/workflows/**'
+      - '.github/actions/**'
+      - '.github/zizmor.yml'
+  pull_request:
+    paths:
+      - '.github/workflows/**'
+      - '.github/actions/**'
+      - '.github/zizmor.yml'
+
+permissions: {}
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  zizmor:
+    name: Zizmor
+    runs-on: ubuntu-latest
+    permissions:
+      security-events: write # Upload SARIF to GitHub Security tab
+      contents: read # Read workflow files for analysis
+      actions: read # Read workflow run metadata
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+
+      - name: Run zizmor
+        uses: zizmorcore/zizmor-action@b1d7e1fb5de872772f31590499237e7cce841e8e # v0.5.3

.github/zizmor.yml

@@ -0,0 +1,5 @@
+rules:
+  unpinned-uses:
+    config:
+      policies:
+        '*': hash-pin