Interface ResumableAudioContext

Minimal structural slice of AudioContext these helpers need — keeps them usable with webkitAudioContext and test doubles.

interface ResumableAudioContext {
    addEventListener?: (type: string, listener: () => void) => void;
    removeEventListener?: (type: string, listener: () => void) => void;
    resume: () => Promise<void>;
    state: string;
}