CI: pin ruff

ruff==0.16.0 (released Jul 23, 2026) emits a new wall of warnings

Author: ev-br

.github/workflows/ruff.yml

@@ -13,7 +13,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install ruff
+          pip install "ruff<0.16"
       # Update output format to enable automatic inline annotations.
       - name: Run Ruff
         run: ruff check --output-format=github .