Corrected core regressions in shell disownment.

Shell disownment is now split between run_code_disowned() and
run_command_disowned(), the latter now used exclusively by GUI-specific
CLI aliases. The @{runnable/code} subtree now replaces the prior
@{runnable/command} subtree, in light of the former's more specifically
applicable nomenclature. Parcel @{if_pathable/keychain} has been
reactivated on startup, largely thanks to path globbing improvements.