Another attempt at one reference for the runner OS

Author: mattpopovich

.github/workflows/ci.yml

@@ -6,13 +6,13 @@ on:
       - '**'  # Runs on all branches
   pull_request:
 
+# YAML anchor for the runner OS
+# These images are arm64 unless specified: https://github.com/actions/runner-images
+x-runner: &runner-os [macos-15] # macOS CI is expensive: [macos-14, macos-15, macos-15-intel, macos-26]
+
 jobs:
   build:
-    runs-on: ${{ matrix.os }}
-    strategy:
-      matrix:
-        # These images are arm64 unless specified: https://github.com/actions/runner-images
-        os: [macos-15] # macOS CI is expensive: [macos-14, macos-15, macos-15-intel, macos-26]
+    runs-on: *runner-os
 
     steps:
     - name: Checkout repository
@@ -64,7 +64,7 @@ jobs:
 
   test:
     needs: build
-    runs-on: ${{ matrix.os }}
+    runs-on: *runner-os
 
     steps:
     - name: Checkout repository