The hierarchy is a free signal
Documents already carry the structure that should steer search. This is why the lineage moved from chunk similarity to hierarchy traversal.
Narrow, then bundle
HiKEY's answer: narrow in two stages, documents → sections (zero LLM calls), then fill the budget core-first. A combination tuned to the industrial setting: thousands of docs, tables and figures, a finite reader budget.
The open question (discussion)
Whichever direction the traversal takes, and however it is trained, it happens over headings and summaries. A fact they fail to carry is invisible to every method here. Who breaks this limit?