Function memory_map_from_index 

pub fn memory_map_from_index(index: &MemoryIndex, limit: usize) -> String

The same map, built from the live BM25 index rather than a record list.

This is the form the runtime uses. The canonical index is already resident, so the map costs one pass over memory rather than a repository read — which matters because it has to be rebuilt whenever the corpus changes, and the corpus changes mid-conversation.