Revert the earlier approach of widening the existing PWM-callback assertions to
accept the new timeMs arg — that masked a contract change rather than fixing it.
Instead, updatePwm now hands the optional timeMs only to listeners that declare
a 3rd parameter (cb.length >= 3) — i.e. the buzzer, which needs the precise
onset time. Plain (pin, dutyCycle) listeners, and the existing
toHaveBeenCalledWith(pin, dutyCycle) tests, see an unchanged 2-arg call, so the
original PwmCallback contract is preserved.
Add a PinManager test locking the dispatch: a 2-param listener stays 2-arg; a
3-param listener receives timeMs.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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