/**
 * Plays an audio blob using an HTMLAudioElement (Decision D-3 — blob URL approach).
 * `fetch()` → buffer full response → `URL.createObjectURL(blob)` → `<audio>.play()`
 *
 * @param blob    Audio data (MP3, Opus, AAC, etc.)
 * @param signal  Optional AbortSignal — resolves immediately on abort
 * @returns Promise that resolves when playback ends or rejects on error/abort
 */
export declare function playBlobAudio(blob: Blob, signal?: AbortSignal): Promise<void>;
/**
 * Converts a non-2xx fetch Response into a typed SpeechError and throws it.
 */
export declare function throwIfNotOk(response: Response): Promise<void>;