fix: delay debounce until after wait milliseconds of quiet

[DSeaStar]

debounce is documented as delaying func until wait milliseconds have elapsed since the last call, matching lodash's trailing debounce. The implementation instead primed last_call to now - wait, so the first invocation ran immediately (throttle-like).

This schedules the call on a daemon threading.Timer. Further calls reset that timer; max_wait still forces an invocation so a continuous burst cannot delay forever. Subsequent calls return the last successful result, as before.

Fixes #167