Persist provider reasoning and assistant text separately on agent_reasoning_audit
(DeepSeekAssistantMessage path), extract diagnosis_run.conclusion, enrich RAG
tool audit (step_id/query/qualityScore), gate empty mysql tools, drop devtools,
and align MVP docs after live E2E verification.
Add current RAG architecture covering MilvusClientV2 hybrid search,
chunk evidence identity, rebuild ops, and update the MVP architecture
index and system overview links.