ci: add zizmor static analysis for the workflows (#1016)

Runs zizmor over .github/workflows and publishes results to the Security tab
via SARIF. Report-only for now (continue-on-error) since the existing
workflows still have findings to clear; a follow-up fixes those and turns this
into a hard gate. Answers the "do we have zizmor setup" question from the
review on #996.

Based this on jupyterlab's own zizmor workflow and put it together with Claude
Code, running zizmor against our workflows locally to confirm it works.

Author: notluquis

.github/workflows/zizmor.yml

@@ -0,0 +1,41 @@
+# Static analysis of the GitHub Actions workflows with zizmor.
+# https://github.com/zizmorcore/zizmor
+name: GitHub Actions security (zizmor)
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: ["**"]
+
+permissions: {}
+
+jobs:
+  zizmor:
+    name: zizmor
+    runs-on: ubuntu-latest
+    permissions:
+      security-events: write # upload-sarif needs this to publish results
+    steps:
+      - name: Checkout
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@cec208311dfd045dd5311c1add060b2062131d57 # v8.0.0
+
+      - name: Run zizmor
+        # Report only for now. The existing workflows still have findings to work
+        # through, so this uploads results to the Security tab instead of failing
+        # the build. Flip to a hard gate once they're cleared. No token is passed,
+        # so zizmor runs offline (skips the online-only audits) and avoids the API
+        # rate limits its docs warn about.
+        continue-on-error: true
+        run: uvx zizmor@1.25.2 --format=sarif . > results.sarif
+
+      - name: Upload SARIF
+        uses: github/codeql-action/upload-sarif@c10b8064de6f491fea524254123dbe5e09572f13 # v4.35.1
+        with:
+          sarif_file: results.sarif
+          category: zizmor