todos: document nudge family — --nudge flag, list-nudges-due, dispatch-nudges
Nudge scheduling (call.py:120-149, 441, 490) was live but the skill only
documented basic add/done/cancel/move. Add the --nudge/-n flag to the
add section with the four accepted formats, then add list-nudges-due
and dispatch-nudges as full sections. Also add a Gotchas block for the
fuzzy-duplicate silent-rejection behavior and the read/mutate split
between list-nudges-due and dispatch-nudges.
Plus Invoke via Bash and expanded TRIGGER.
Part of skills audit req_loq3e2lk pass 1+2.