refactor(imports): load traceback on demand for infrequent usage
feat(triggers): add initial support for FEATURES=protect-owned
fix(triggers): show full pkg -> file list mapping for protect-owned

Previously it would only show the first pkg owning some of the colliding
files.
style(merge/triggers): don't strictly adhere to <80 column line lengths

Allow up to 100 or so columns mostly to improve readability and flow.