Enhancement: Speed up keyword searches against history names

Keyword searches are slow. Especially with many histories. Perhaps it is not just searching the history names and trying to load more content and this slows it down?

Start by reproducing keyword searches with many histories and tracing whether the search loads history content beyond names. Identify the relevant search path from that investigation, then compare search behavior and timing before and after the change. Done means searches remain correct and are measurably faster for large history collections.

Written by the indexing model from the issue text.