Research Assistant Pipeline

Implement research_assistant(query, search_fn, extract_fn, synthesize_fn). - Call search_fn(query) to retrieve a list of source dicts. Each source has {"id": str, "content": str}. - If search returns an empty list, return {"error": "no sources found", "sources": []}. - For each source with non-empty content, call extract_fn(source) to get extracted data. - If extract_fn returns None, skip that source entirely. - Each successful extraction must preserve its source identity: {"source_id": source["id"], "data": <extracted_value>}. - Collect all successful extractions into an extracted list. - If no extractions succeeded, return {"error": "no data extracted", "sources": sources}. - Otherwise call synthesize_fn(extracted) to produce the final synthesis. - Return {"result": synthesis, "sources": sources, "extracted": extracted, "source_count": len(sources)}.