fix: keep relevance scores on knowledge tool citations (#31307)

With native function calling, citations produced by query_knowledge_files and query_chat_files never showed the relevance percentage badge, while the same knowledge base queried through classic RAG did.

The tools already return a distance per chunk, but the step that groups tool results into citation sources dropped it. Each grouped source now carries a distances list aligned with its documents, the same shape the classic RAG path emits, so the existing citation UI shows the badge without frontend changes. Chunks without a score (notes) leave the list empty, which the UI already treats as no score.

Fixes #29776

backend/open_webui/utils/middleware.py

@@ -510,6 +510,7 @@ def get_citation_source_from_tool_result(
                         },
                         'document': [],
                         'metadata': [],
+                        'distances': [],
                     }
 
                 sources_by_file[key]['document'].append(content)
@@ -521,6 +522,8 @@ def get_citation_source_from_tool_result(
                         **({'note_id': note_id} if note_id else {}),
                     }
                 )
+                if 'distance' in chunk:
+                    sources_by_file[key]['distances'].append(chunk['distance'])
 
             # Return all grouped sources as a list
             if sources_by_file: