Fix (beta): don't batch permissions for tantivy search results

UnifiedSearchViewSet.list() returns SearchHit/dict-like objects for
text/title/query/more_like_id search requests, not Document ORM instances.
Adding BulkPermissionMixin to DocumentViewSet (previous commit) meant its
get_serializer_context() ran for search responses too, and its
_get_object_perms() -- which expects real model instances with .pk --
crashed on the dict-like hits with AttributeError, turning every search
request into a 400.

Skip the batching specifically for search requests (existing
_is_search_request() check) by calling past BulkPermissionMixin in the
MRO; non-search list() calls (which return a real Document queryset) are
unaffected and still get the batching.

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

src/documents/views.py

@@ -2290,6 +2290,15 @@ class UnifiedSearchViewSet(DocumentViewSet):
             return SearchResultSerializer
         return DocumentSerializer
 
+    def get_serializer_context(self):
+        if self._is_search_request():
+            # BulkPermissionMixin.get_serializer_context() (inherited via
+            # DocumentViewSet) assumes it's batching permissions for a page of
+            # real Document instances. Tantivy search results are SearchHit/
+            # dict-like objects instead, so skip straight past it here.
+            return super(BulkPermissionMixin, self).get_serializer_context()
+        return super().get_serializer_context()
+
     def _get_active_search_params(self, request: Request | None = None) -> list[str]:
         request = request or self.request
         return [