Fix CI: Add setup-python to lint job

The lint job was missing actions/setup-python, causing the
generate_opcode_metadata.py script to run with the default system
Python which may not have itertools.batched (Python 3.12+).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: youknowone

.github/workflows/ci.yaml

@@ -452,6 +452,10 @@ jobs:
       - name: Ensure docs generate no warnings
         run: cargo doc
 
+      - uses: actions/setup-python@v6.2.0
+        with:
+          python-version: ${{ env.PYTHON_VERSION }}
+
       - name: Ensure Lib/_opcode_metadata is updated
         run: |
           python scripts/generate_opcode_metadata.py