Moves three contiguous quest mutation handlers (--add-quest,
--add-quest-objective, --remove-quest-objective) out of
main.cpp into a new cli_quest_objective.{hpp,cpp} module.
All three operate on a zone's quests.json with the same
QuestEditor load-edit-save flow; the objective add/remove
pair includes auto-generated description text from
type+name+count for tooltip-friendly defaults.
main.cpp shrinks by 174 lines (6,603 to 6,429). Reward and
clone-quest handlers stay inline for follow-up extractions.
