Three bugs caused 'Chunk by Question' to silently produce token chunks:
1. QuestionChunkingStrategy.chunk_pages() had a broken event-loop check
that always skipped LLM structure detection in FastAPI's async context.
Fixed by making chunk_pages() async and removing the is_running() guard.
2. get_chunking_strategy() factory never passed an LLMClient to
QuestionChunkingStrategy. Fixed by creating LLMClient in the factory
with graceful fallback to regex-only when config is incomplete.
3. rag.list_documents() and list_chunks() didn't extract strategy_type
or Q&A fields from ChromaDB metadata, so the frontend always showed
chunking_strategy='token' and null Q&A fields. Fixed by reading
these fields from ChromaDB and routing them through the API.
Also: TokenChunkingStrategy.chunk_pages() made async for consistency
with the question strategy; ingest router updated to await it.
Tests updated (asyncio.run() for sync tests, async mock chunk_pages).
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