xcode 26 -- coupled with macos15 update!

Author: shepmaster

src/ci/github-actions/jobs.yml

@@ -95,7 +95,7 @@ envs:
     PR_CI_JOB: 1
 
   env-macos-xcode: &env-macos-xcode
-    SELECT_XCODE: /Applications/Xcode_15.4.app
+    SELECT_XCODE: /Applications/Xcode_26.app
     USE_XCODE_CLANG: 1
 
   # Ensure that host tooling is tested on our minimum supported macOS