Create lib.rs so all binaries can share library code directly instead
of shelling out to poc-memory. memory-search now calls search::search()
and store::Store::load() in-process instead of Command::new("poc-memory").
The load-context call still shells out (needs get_group_content moved
from main.rs to a library module).
Also: add search::format_results(), deduplicate extract_query_terms.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
