* perf(hopper): resolve string search records once per query
search_strings called _string_inventory(document) once per match, and each
call sorts every string address and rebuilds the record dict, so a query cost
O(matches x strings log strings). Resolve the inventory once per search.
Warm search, 50% matches, fake document, best of 7: 1000 strings 186 -> 0.5 ms,
4000 strings 3161 -> 2.1 ms, 8000 strings 13121 -> 4.9 ms; output byte-identical.
* perf(hopper): skip record resolution for empty string searches
Resolving the full string inventory for a query with no matches added a sort
of every string address that the previous code never performed. Return early
when nothing matches. Zero-match search on a warm document, best of 7:
64000 strings 35.9 ms before this change, 4.0 ms after (main: 3.9 ms).
keemsisi