Fix workflow issues reported by zizmor.

Author: davidlehn

.github/workflows/main.yaml

@@ -2,12 +2,16 @@ name: Main CI
 
 on: [push]
 
+permissions: {}
+
 jobs:
   lint:
     runs-on: ubuntu-latest
     timeout-minutes: 10
     steps:
     - uses: actions/checkout@v5
+      with:
+        persist-credentials: false
     - uses: actions/setup-python@v6
       with:
         python-version: '3.14'
@@ -38,6 +42,8 @@ jobs:
         loader: [requests, aiohttp]
     steps:
     - uses: actions/checkout@v5
+      with:
+        persist-credentials: false
     - name: Use Python ${{ matrix.python-version }}
       uses: actions/setup-python@v6
       with: