fix: Use Python 3.12 for pyright workflow to match requires-python constraint

pyproject.toml declares requires-python = ">=3.9,<3.13", so Python 3.13
is not a supported version. Use 3.12 instead.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jamt9000

.github/workflows/pyright.yml

@@ -15,7 +15,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: '3.13'
+          python-version: '3.12'
 
       - name: Install dependencies
         run: |