add free security workflows (semgrep + npm audit + gitleaks, codeql when public)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: ralyodio

.github/workflows/codeql.yml

@@ -0,0 +1,40 @@
+# CodeQL is FREE on public repos. On private repos the SARIF upload step
+# requires GitHub Advanced Security. This job auto-skips when the repo is
+# private so the workflow doesn't fail loudly — flip the repo public and it
+# runs automatically.
+
+name: codeql
+
+on:
+  pull_request:
+    branches: [master, main]
+  push:
+    branches: [master, main]
+  schedule:
+    - cron: "21 4 * * 1"
+
+jobs:
+  analyze:
+    name: analyze (${{ matrix.language }})
+    if: ${{ github.event.repository.visibility == 'public' }}
+    runs-on: ubuntu-latest
+    permissions:
+      actions: read
+      contents: read
+      security-events: write
+
+    strategy:
+      fail-fast: false
+      matrix:
+        language: [javascript-typescript]
+
+    steps:
+      - uses: actions/checkout@v4
+      - uses: github/codeql-action/init@v3
+        with:
+          languages: ${{ matrix.language }}
+          queries: security-and-quality
+      - uses: github/codeql-action/autobuild@v3
+      - uses: github/codeql-action/analyze@v3
+        with:
+          category: "/language:${{ matrix.language }}"

.github/workflows/security.yml

@@ -0,0 +1,58 @@
+name: security
+
+on:
+  pull_request:
+    branches: [master, main]
+  push:
+    branches: [master, main]
+  schedule:
+    - cron: "11 6 * * 1"
+
+jobs:
+  semgrep:
+    name: semgrep
+    runs-on: ubuntu-latest
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository
+    container:
+      image: semgrep/semgrep
+    steps:
+      - uses: actions/checkout@v4
+      - run: |
+          semgrep scan --error --severity ERROR \
+            --config p/javascript \
+            --config p/typescript \
+            --config p/owasp-top-ten \
+            --config p/secrets
+
+  npm-audit:
+    name: npm audit
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+      - name: Audit (skip when no package.json)
+        run: |
+          if [ -f package.json ]; then
+            (npm ci --no-audit --no-fund 2>/dev/null || npm install --no-audit --no-fund)
+            npm audit --audit-level=high
+          else
+            echo "no package.json — skipping npm audit"
+          fi
+
+  gitleaks:
+    name: gitleaks
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - name: Install gitleaks
+        run: |
+          VERSION=8.21.2
+          curl -sSL "https://github.com/gitleaks/gitleaks/releases/download/v${VERSION}/gitleaks_${VERSION}_linux_x64.tar.gz" \
+            | tar -xz -C /usr/local/bin gitleaks
+          gitleaks version
+      - name: Scan history
+        run: gitleaks detect --source . --redact --verbose --no-banner --exit-code 1