Retrieve what a mind knows about a query

Everything this mind holds that bears on the query: matched skills, remembered facts, and document excerpts.

This endpoint does not generate text. All three arms are existing non-generative retrievers, scoped to the mind. The caller does the reasoning — which is the point, since a model is usually already sitting on the other side of this call.

Arms fail independently: a dead embedder costs you skills and excerpts, not the memories you could still have had.