UID2-7011: add zizmor workflow-security scan (report-only)

Bare caller of the shared scan: severity floors inherit central defaults
(report-only, High) and are overridable per-repo via ZIZMOR_* Actions
variables. Part of the UID2-7011 org-wide rollout.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: swibi-ttd

.github/workflows/zizmor.yaml

@@ -0,0 +1,20 @@
+name: Zizmor Scan
+
+on:
+  pull_request:
+    # Trigger when anything zizmor scans changes. The scan itself covers the
+    # whole repo; if this repo keeps composite actions outside .github/, add
+    # those paths so changes there don't slip through.
+    paths:
+      - '.github/**'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  zizmor:
+    # Bare call: severity floors inherit the shared workflow's central defaults
+    # (report-only, High), so org-wide retunes are a single change in
+    # uid2-shared-actions. See the zizmor section of its README.
+    uses: IABTechLab/uid2-shared-actions/.github/workflows/shared-zizmor-scan.yaml@v3