fix: properly handle Python 3.13 support with PyTorch compatibility

- Support Python 3.13 on most platforms (Ubuntu, ARM64 Mac)
- Exclude Intel Mac + Python 3.13 combination due to PyTorch wheel availability
- PyTorch <2.5 supports Intel Mac but not Python 3.13
- PyTorch 2.5+ supports Python 3.13 but not Intel Mac x86_64
- Document limitation in CI configuration comments
- Update README badges with detailed Python version support and CI status

🤖 Generated with [Claude Code](https://claude.ai/code)

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

.github/workflows/build-reusable.yml

@@ -72,8 +72,8 @@ jobs:
             python: '3.11'
           - os: macos-13
             python: '3.12'
-          - os: macos-13
-            python: '3.13'
+          # Note: macos-13 + Python 3.13 excluded due to PyTorch compatibility
+          # (PyTorch 2.5+ supports Python 3.13 but not Intel Mac x86_64)
     runs-on: ${{ matrix.os }}
 
     steps: