Replace deprecated macos-13 runner with macos-15-intel

GitHub is deprecating macos-13 runners (brownout started Sept 2025,
full deprecation by Dec 2025). Replace with macos-15-intel to build
Intel macOS wheels. This produces the same x86_64 wheels but uses the
supported runner image.

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

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

Author: asmeurer

.github/workflows/publish-package.yml

@@ -73,8 +73,8 @@ jobs:
     needs: [build_sdist]
     strategy:
       matrix:
-        # macos-13 is an intel runner, macos-14 is apple silicon
-        os: [ubuntu-latest, ubuntu-24.04-arm, windows-latest, macos-13, macos-14]
+        # macos-15-intel is an intel runner, macos-14 is apple silicon
+        os: [ubuntu-latest, ubuntu-24.04-arm, windows-latest, macos-15-intel, macos-14]
 
     steps:
       - uses: actions/checkout@v5