Archive a completed work item by moving its directory into the archive
with a date and type prefix. Marks the work item as done: the lifecycle
state of a work item is its directory location — under changes/type/
it is active, under changes/archive/YYYY-MM-DD-type-name/ it is
archived. Trigger: "fullstack archive", "archive it", "归档",
"做完了", "ship it", "结了", "merged", "已完成", "收尾". Use when the
user says a feature, fix, or refactor is done, shipped, merged, or
finished and should be moved out of the active listing.
