Try macos 26 runner

Author: mcbarton

.github/workflows/main.yml

@@ -202,8 +202,8 @@ jobs:
         include:
           - name: ubu24
             os: ubuntu-24.04
-          - name: osx15-arm
-            os: macos-15
+          - name: osx26-arm
+            os: macos-26
 
     steps:
       - uses: actions/checkout@v5