Change test workflow to run on macos-15 for Xcode 16+ default

feature/swift-testing

Author: roanutil

.github/workflows/ci.yml

@@ -26,7 +26,7 @@ jobs:
       - name: Lint
         run: swiftlint lint --quiet
   test:
-    runs-on: macos-latest
+    runs-on: macos-15
     environment: default
     steps:
       - uses: actions/checkout@v4