ci: use namespace runners for windows jobs (#11864)

Switch the two Windows CI jobs (build-examples-cmake-windows and
build-libghostty-vt-windows) from GitHub-hosted windows-2025 runners to
namespace-profile-ghostty-windows runners.

.github/workflows/test.yml

@@ -271,7 +271,7 @@ jobs:
       matrix:
         dir: ${{ fromJSON(needs.list-examples.outputs.cmake) }}
     name: Example ${{ matrix.dir }} (Windows)
-    runs-on: windows-2025
+    runs-on: namespace-profile-ghostty-windows
     timeout-minutes: 45
     needs: [test, list-examples]
     steps:
@@ -526,7 +526,7 @@ jobs:
           ANDROID_NDK_HOME: ${{ steps.setup-ndk.outputs.ndk-path }}
 
   build-libghostty-vt-windows:
-    runs-on: windows-2025
+    runs-on: namespace-profile-ghostty-windows
     timeout-minutes: 45
     needs: test
     steps: