Job_chat: RAG does not re-run when the user navigates from one job to another

Lightning rebuilds conversation histories from previous conversation turns, instead of using the history key returned by Apollo. This means that RAG is not re-triggered when a user navigates from one step to another. Check the impact of this (if it's just general documentation, it might not be too bad) and consider giving job_chat access to the documentation tool the planner already uses instead.

Start by tracing job_chat's conversation-history handling and compare it with the history key returned by Apollo. Then inspect how the planner accesses the documentation tool. Determine whether navigation between steps affects only documentation or broader RAG behavior, and record the impact and the justified scope of any change.