Run CI steps whatever the runner's execution policy

Co-Authored-By: Claude Opus 5.5 <[email protected]>

.gitea/workflows/ci.yml

@@ -17,7 +17,8 @@ jobs:
     runs-on: windows
     defaults:
       run:
-        shell: powershell
+        # Steps run as script files, which Windows' default execution policy refuses.
+        shell: powershell -NoProfile -ExecutionPolicy Bypass -Command ". '{0}'"
     steps:
       - name: Check out
         env: