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>