Add a browser-side model for top-level history entries and history step
coordinates. This gives the UI process a structure to mirror WebContent
history across process swaps.
Add debug dumping support alongside the model so traversal state can be
inspected while working on back and forward behavior.
Teach LibWebView autocomplete to query HistoryStore before falling back
to remote engines and move the wiring out of the AppKit frontend.
Refine matching so scheme and www. boilerplate do not dominate results,
short title and substring queries stay quiet, and history tracing can
explain what the ranking code is doing.