watch

Internal sweep-and-report skill for auto-watching dispatched legate children. Armed by `legate:dispatch` at launch time and fired on a cadence by `ScheduleWakeup`. Sweeps only the children tagged `@legate-parent = <my pane id>`, hashes each pane tail, reports deltas via `legate:debrief`, and re-schedules the next tick. Also handles user utterances that stop or confirm watching: "stop watching", "cancel the watcher", "enough watching", "are you still watching?", "watch my legates" (confirmation when children exist; a hint to dispatch when none do). Do NOT invoke for "start watching" — watching is implicit in dispatch.