fix: Use _path_add for PATH entries appended at the end

profile.d/path and rc.d/rvm concatenated onto PATH directly, so
re-sourcing them in the same shell (source ~/.bashrc, a resourced
tmux pane, etc.) would duplicate entries. _path_add already guards
against that and tests directory existence itself.

profile.d/krew and profile.d/anyenv are left untouched: they prepend
to PATH (to take priority over other entries), while _path_add always
appends — converting them would silently change resolution order.

rc.d/rvm

@@ -5,4 +5,4 @@
 [[ -r "${HOME}/.rvm/scripts/completion" ]] && source "${HOME}/.rvm/scripts/completion"
 
 # Add RVM to PATH for scripting
-[[ -r "${HOME}/.rvm/bin" ]] && PATH="${PATH}:${HOME}/.rvm/bin"
+[[ -r "${HOME}/.rvm/bin" ]] && _path_add "${HOME}/.rvm/bin"