fix(0.6.1): pipeline firstMessage barge-in aborts TTS stream + unblocks LLM

[nicolotognoni]

Summary

• Fixes a critical pipeline-mode bug where interrupting the agent during the firstMessage left the call silent: cancelSpeaking flipped isSpeaking=false but the for await over tts.synthesizeStream stayed suspended on the provider WS until FRAME_TIMEOUT_MS (30 s on ElevenLabs WS), so no subsequent LLM turn ever dispatched even though Deepgram kept transcribing.
• Adds an abort signal raced against the iterator's next() / __anext__ plus an optional TTSAdapter.cancel() hook that closes the in-flight provider WS, so the firstMessage loop exits within one event-loop tick on barge-in.
• Full parity Python ↔ TypeScript: firstMessageAbort / _first_message_abort, activeSocket / _active_socket, cancel() on both ElevenLabsWebSocketTTS implementations.

Implementation

• libraries/typescript/src/stream-handler.ts
  • New private field firstMessageAbort: AbortController | null.
  • cancelSpeaking() now also calls firstMessageAbort.abort().
  • Replaced the firstMessage for await with a manual async-iterator loop racing iter.next() against the abort signal; on abort calls this.tts?.cancel?.() then awaits iter.return() to drive the generator's finally.
• libraries/typescript/src/provider-factory.ts — added optional cancel?() method on TTSAdapter.
• libraries/typescript/src/providers/elevenlabs-ws-tts.ts — track activeSocket across synthesizeStream, add cancel() that closes it, fold cancel() into close().
• libraries/python/getpatter/stream_handler.py
  • New field self._first_message_abort: asyncio.Event | None.
  • _do_cancel_for_barge_in sets the abort event and calls tts.cancel() when the adapter exposes it.
  • Replaced the firstMessage async for with a manual asyncio.wait race of __anext__ against fm_abort.wait(); agen.aclose() always runs in finally.
• libraries/python/getpatter/providers/elevenlabs_ws_tts.py — track self._active_socket across synthesize, add cancel() that schedules ws.close() on the loop, catch ConnectionClosed in the recv loop as end-of-stream.
• Regression tests added in both SDKs: _handle_barge_in sets abort event + invokes tts.cancel when available, plus a standalone iterator-race test that proves a stalled generator unblocks within one tick of (abort + adapter.cancel).
• CHANGELOG.md ## 0.6.1 ### Fixed entry.

Breaking change?

No. The new TTSAdapter.cancel() is optional — existing adapters without it are unaffected (the stream handler null-checks before calling). All existing public API shapes are preserved.

Test plan

• Python: pytest tests/ — 1845 passed, 7 skipped, 0 failed.
• TypeScript: npx vitest run — 1518 passed, 0 failed.
• TypeScript: npm run lint (tsc --noEmit) — clean.
• TypeScript: npx tsup build — success.
• Manual: place an outbound pipeline-mode call with Deepgram STT + Cerebras LLM + ElevenLabsWebSocketTTS, interrupt the agent ~500 ms into the firstMessage, confirm the next user turn dispatches an LLM response (no 30 s silence, no FRAME_TIMEOUT_MS error).

Docs updates

N/A — internal fix, no public API surface change beyond the optional cancel() hook (which is documented inline in the TTSAdapter interface).