defense-in-depth improvements to GitHub actions workflows

.github/workflows/clang-format.yaml

@@ -1,13 +1,18 @@
 name: Check clang-format
 on: [push, pull_request]
+permissions:
+  contents: read
 jobs:
   formatting-check:
     name: Formatting Check
     runs-on: 'ubuntu-24.04'
+
     steps:
-    - uses: actions/checkout@v6
+    - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+      with:
+        persist-credentials: false
     - name: Run clang-format style check for C/C++/Protobuf programs.
-      uses: jidicula/clang-format-action@v4.17.0
+      uses: jidicula/clang-format-action@654a770daa28443dd111d133e4083e21c1075674 # v4.18.0
       with:
         clang-format-version: '21'
         fallback-style: 'Google' # optional

.github/workflows/main.yml

@@ -13,6 +13,9 @@ on:
   # Allows you to run this workflow manually from the Actions tab
   workflow_dispatch:
 
+permissions:
+  contents: read
+
 # A workflow run is made up of one or more jobs that can run sequentially or in parallel
 jobs:
   # This workflow contains a single job called "build"
@@ -23,7 +26,9 @@ jobs:
     # Steps represent a sequence of tasks that will be executed as part of the job
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+        with:
+          persist-credentials: false
 
       - name: Install extra packages
         run: |