fix(search): complete the query error surface across every endpoint

Four pieces of the same surface:

whoosh-compat's emit() documents a two-part host contract: both a parse
diagnostic and the QueryEmitError/UnsupportedQueryError pair are
user-input errors. Only the latter half was caught; QueryEmitError now
maps to SearchQueryError too. Messages pass through a cleanup that
strips the library's DIVERGENCES.md references and replaces the
fast=True host-configuration advice with user language, so no
library-internal vocabulary reaches a searching user.

The bulk selection paths (bulk edit, the legacy bulk endpoint, bulk
download) reached the backend with no SearchQueryError handler, so a
bad date or number in a selection filter raised straight to a DRF 500.
They now share the search list endpoint's exact mapping (a new
search_query_error_messages helper flattens MultipleSearchQueryErrors
in one place), returning the same 400 body for the same bad query.

QueryParserError means a whoosh-compat parser bug, not user-fixable
input, per its own contract; the list endpoint's blanket handler was
converting it to a generic 400. It now re-raises and surfaces as a 500
that monitoring can see.

All behavior is pinned test-first: bulk edit and bulk download API
tests assert 400s naming the bad value (previously unhandled
exceptions), a unit test pins the QueryEmitError mapping, three
parametrized checks assert no internal vocabulary leaks for the
unsupported query shapes, and a mocked parser-bug test asserts the 500.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WMsn6DgzbvSqh1pwy66VVF

src/documents/views.py

@@ -2416,12 +2416,14 @@ class UnifiedSearchViewSet(DocumentViewSet):
         if not self._is_search_request():
             return super().list(request)
 
-        from documents.search import MultipleSearchQueryErrors
+        from whoosh_compat.errors import QueryParserError
+
         from documents.search import SearchHit
         from documents.search import SearchQueryError
         from documents.search import TantivyBackend
         from documents.search import TantivyRelevanceList
         from documents.search import get_backend
+        from documents.search import search_query_error_messages
 
         def parse_search_params() -> SearchParams:
             """Extract query string, search mode, and ordering from request."""
@@ -2615,12 +2617,12 @@ class UnifiedSearchViewSet(DocumentViewSet):
             # User-fixable query error(s) (e.g. unparsable dates/numbers):
             # surface every offending field's message, not just the first,
             # so the user can fix them all in one round-trip.
-            messages = (
-                [str(sub) for sub in e.errors]
-                if isinstance(e, MultipleSearchQueryErrors)
-                else [str(e)]
-            )
-            raise ValidationError({"query": messages}) from e
+            raise ValidationError({"query": search_query_error_messages(e)}) from e
+        except QueryParserError:
+            # A whoosh-compat parser BUG (its own contract: not user-fixable
+            # input). Let it surface as a 500 monitoring can see instead of
+            # a 400 blaming the user for a library defect.
+            raise
         except Exception as e:
             logger.warning(f"An error occurred listing search results: {e!s}")
             return HttpResponseBadRequest(
@@ -2767,17 +2769,29 @@ class DocumentSelectionMixin:
         backend = get_backend()
         search_user = None if user.is_superuser else user
 
-        if filter_name == "more_like_id":
-            more_like_doc_id = _get_more_like_id(filters, user)
+        from documents.search import SearchQueryError
+        from documents.search import search_query_error_messages
 
-            search_ids = backend.more_like_this_ids(more_like_doc_id, user=search_user)
-        else:
-            query_str, search_mode = _get_tantivy_query_and_mode(filters)
-            search_ids = backend.search_ids(
-                query_str,
-                user=search_user,
-                search_mode=search_mode,
-            )
+        try:
+            if filter_name == "more_like_id":
+                more_like_doc_id = _get_more_like_id(filters, user)
+
+                search_ids = backend.more_like_this_ids(
+                    more_like_doc_id,
+                    user=search_user,
+                )
+            else:
+                query_str, search_mode = _get_tantivy_query_and_mode(filters)
+                search_ids = backend.search_ids(
+                    query_str,
+                    user=search_user,
+                    search_mode=search_mode,
+                )
+        except SearchQueryError as e:
+            # Same user-fixable-query mapping as the search list endpoint:
+            # a bad date/number in a bulk selection filter is a 400 naming
+            # the value, never a 500.
+            raise ValidationError({"query": search_query_error_messages(e)}) from e
 
         return search_ids