Fix release CI: replace deprecated macos-13 with macos-latest

macos-13 runner is no longer supported on GitHub Actions.
Use macos-latest for both x86_64 (cross-compiled) and aarch64 (native).

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

Author: cigrainger

.github/workflows/release.yml

@@ -19,7 +19,7 @@ jobs:
             target: x86_64
           - os: ubuntu-latest
             target: aarch64
-          - os: macos-13
+          - os: macos-latest
             target: x86_64
           - os: macos-latest
             target: aarch64