Switch CI to Xcode 26.2 for Swift 6.2 support

Author: claude

.github/workflows/ci.yml

@@ -18,9 +18,7 @@ jobs:
     runs-on: macOS-15
     steps:
       - uses: actions/checkout@v4
-      - name: Xcode Select Version
-        uses: mobiledevops/xcode-select-version-action@v1
-        with:
-          xcode-select-version: 16.4
+      - name: Select Xcode 26.2
+        run: sudo xcode-select -s /Applications/Xcode_26.2.app/Contents/Developer
       - name: Test
         run: set -o pipefail && swift test | xcbeautify --renderer github-actions