Add check on macos-26

Author: remlapmot

.github/workflows/check-full.yaml

@@ -28,6 +28,7 @@ jobs:
       # max-parallel: 2
       matrix:
         config:
+          - {os: macos-26,   r: 'release'}
           - {os: macos-15,   r: 'release'}
           - {os: windows-latest, r: 'release'}
           - {os: ubuntu-latest,   r: 'release'}