ci: add workflow lint and whitespace checks

Co-Authored-By: Codex <noreply@openai.com>

Author: Pigbibi

.github/workflows/ci.yml

@@ -7,6 +7,18 @@ on:
       - main
 
 jobs:
+  actionlint:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    permissions:
+      contents: read
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v6
+
+      - name: Actionlint
+        uses: docker://rhysd/actionlint:1.7.12
+
   test:
     runs-on: ubuntu-latest
     permissions:
@@ -15,6 +27,16 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v6
 
+      - name: Check whitespace
+        run: |
+          set -euo pipefail
+          if [ "${{ github.event_name }}" = "pull_request" ]; then
+            git fetch --no-tags --depth=1 origin "${{ github.base_ref }}"
+            git diff --check "origin/${{ github.base_ref }}...HEAD"
+          else
+            git diff-tree --check --no-commit-id --root -r HEAD
+          fi
+
       - name: Set up Python
         uses: actions/setup-python@v6
         with: