ci: switch CodeQL to advanced setup so fixture paths can be excluded

.github/codeql/codeql-config.yml

@@ -0,0 +1,9 @@
+name: codeguard CodeQL config
+
+# codeguard's test suites detect vulnerabilities in deliberately vulnerable
+# fixture files. Excluding those paths keeps CodeQL and Copilot Autofix from
+# flagging the fixtures themselves (and suggesting "fixes" that would defang
+# the detection corpus).
+paths-ignore:
+  - "**/testdata/**"
+  - "tests/corpus/**"

.github/workflows/codeql.yml

@@ -0,0 +1,56 @@
+name: CodeQL
+
+# Advanced CodeQL setup, replacing GitHub default setup. The advanced setup
+# exists so .github/codeql/codeql-config.yml can exclude codeguard's
+# deliberately vulnerable test fixtures (testdata/, tests/corpus/) — default
+# setup does not support path exclusions.
+
+on:
+  push:
+    branches:
+      - main
+      - develop
+  pull_request:
+    branches:
+      - main
+      - develop
+  schedule:
+    # Weekly, matching the cadence default setup used.
+    - cron: "30 5 * * 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: actions
+            build-mode: none
+          - language: go
+            build-mode: autobuild
+          - language: javascript-typescript
+            build-mode: none
+    steps:
+      - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@e8e8e51caba890f74f97e228d00b0b81b666ee4c # v3
+        with:
+          languages: ${{ matrix.language }}
+          build-mode: ${{ matrix.build-mode }}
+          config-file: ./.github/codeql/codeql-config.yml
+
+      - name: Perform CodeQL analysis
+        uses: github/codeql-action/analyze@e8e8e51caba890f74f97e228d00b0b81b666ee4c # v3
+        with:
+          category: "/language:${{ matrix.language }}"