pub fn register_search_ex_command(registry: &mut CommandRegistry)Expand description
K.2.5 (2026-06-02): register the :search <query> ex-command.
Relocated from crates/lattice-host/src/multibuffer_keymap.rs::register_search_ex_command
as part of the K.2.5 migration. Boot path in editor_boot.rs
calls this directly now; behaviour preserved verbatim.
Stashes the query as Args::String and routes through
AppEffect::SearchTrigger { query }. M.10.6 (2026-06-03)
inlined the work into the host’s apply_effect arm; the
previous Action::SearchTrigger + Editor::do_search hops
are gone. Empty query is rejected with BadArgs — opening
an empty search view doesn’t make sense.