Fix: update macOS-13 to macOS-14 runner

macOS-13 runners are retired per GitHub announcement.

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

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

Author: Jonathan D.A. Jewell

.github/workflows/release.yml

@@ -36,7 +36,7 @@ jobs:
             archive: tar.gz
             cross: true
           - target: x86_64-apple-darwin
-            os: macos-13
+            os: macos-14
             artifact: proof-of-work
             archive: tar.gz
           - target: aarch64-apple-darwin