ci: run Windows tests on Namespace runner

Co-authored-by: GPT-5 Codex <codex@openai.com>

Author: wan9chi

.github/workflows/ci.yml

@@ -237,7 +237,7 @@ jobs:
           - shard: windows-ignored
             partition: ''
             mode: ignored
-    runs-on: windows-latest
+    runs-on: namespace-profile-windows-4c-8g
     env:
       PARTITION: ${{ matrix.partition }}
     steps: