Report drift in the pinned Roblox payload metadata

Two kinds of drift only surface when a user hits them. The compatibility
catalog falls behind what the provider publishes, so new installs land on
a version Roblox has since retired; and the preferred supported profile
loses its pinned bootstrap source, so the pinned bootstrap path cannot
produce the version the updater falls back to.

Add a checker that reports both, and run the existing script unit tests in
CI, where they were never executed.

Run against this tree the checker already reports real drift: the
preferred profile 2.727.1199 has no pinned bootstrap source. Pinning one
means downloading and hashing the archive, and a newer profile also needs
a graphics canary on real hardware, so this reports the condition rather
than pretending to fix it.

The checker stays a plain script that anyone can run on demand; no
scheduled workflow is added.

.github/workflows/ci.yml

@@ -52,6 +52,12 @@ jobs:
           find config packaging/flatpak -type f -name '*.json' -print0 \
             | xargs -0 -n1 python3 -m json.tool >/dev/null
 
+      - name: Run script unit tests
+        shell: bash
+        run: |
+          python3 -m pip install --disable-pip-version-check requests
+          python3 -m unittest discover -s tests -p '*_test.py' -v
+
       - name: Verify build and packaging contracts
         shell: bash
         run: |