Previously the palette only opened after pressing Enter because the trigger
logic lived in the KeyEnter branch. The spec requires '/' to open the palette
immediately. Now KeyRunes with '/' as the first character of an empty input
switches to statePalette right away, carrying any trailing characters (e.g.
'/iss') as the initial search query.
Adds regression tests covering: immediate '/', '/' with query, and ordinary
text staying in input state.
刘焱