Release CI: macOS job on the org macos-release runner

The standard macOS runners are shared with all CI and queue for an hour or
more. The macos-release runner (GitHub-hosted M2 Pro) is in a runner group
usable only by release.yml on the release branch, with a monthly spend cap
on the actions_macos_xl SKU.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/release.yml

@@ -74,7 +74,7 @@ jobs:
   macos:
     name: macOS universal
     needs: version
-    runs-on: macos-15
+    runs-on: macos-release  # org larger runner (M2 Pro), release.yml@release only; capped by the actions_macos_xl budget
     environment: release
     env:
       DECKCRAFT_VERSION: ${{ needs.version.outputs.version }}