ci: add CodeQL workflow for Python static analysis

.github/workflows/codeql.yml

@@ -0,0 +1,44 @@
+name: CodeQL
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+  schedule:
+    # Weekly on Monday at 06:00 UTC — catches advisories that landed
+    # without a corresponding code change in this repo.
+    - cron: '0 6 * * 1'
+
+permissions:
+  contents: read
+
+jobs:
+  analyze:
+    name: Analyze (${{ matrix.language }})
+    runs-on: ubuntu-latest
+    permissions:
+      security-events: write
+      packages: read
+      actions: read
+      contents: read
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - language: python
+            build-mode: none
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
+
+      - uses: github/codeql-action/init@53e96ec3b35fce51c141c0d6f0e31028a448722d  # v3
+        with:
+          languages: ${{ matrix.language }}
+          build-mode: ${{ matrix.build-mode }}
+          queries: security-extended,security-and-quality
+
+      - uses: github/codeql-action/analyze@53e96ec3b35fce51c141c0d6f0e31028a448722d  # v3
+        with:
+          category: "/language:${{ matrix.language }}"