detectTrigger split an `@folder:apps/desk` token into one opaque query, so
every consumer downstream had to re-parse the prefix — or, more often, treat
it as characters the user was expected to maintain by hand.
Split it into `scope` + `value` at the source, behind a known-kinds list so a
handle like @teknium1: or a host:port stays ordinary text, and add
openDirectiveScope() for callers that need to know the caret is sitting in an
empty scope.
Brooklyn Nicholson
fb5efe917a