fix: include hidden files in preview build artifact (closes #469)

The search index lives in docs/dist/.vocs/ (a hidden directory).
actions/upload-artifact@v4 excludes hidden files by default, so the
.vocs directory was missing from the uploaded artifact. This caused
the search index to be absent from preview deployments, breaking the
native search (/) on all preview URLs.

Adding include-hidden-files: true ensures the .vocs directory (and
any other hidden assets) are included in the artifact.

Author: frameworks-volunteer

.github/workflows/preview-build.yml

@@ -41,5 +41,6 @@ jobs:
         with:
           name: preview-build
           path: docs/dist
+          include-hidden-files: true
           if-no-files-found: error
           retention-days: 1