Pipeline.run() used asyncio.gather, so if one loop raised, the failing
coroutine propagated while the sibling loops kept running detached; aclose()
in the finally then closed a source/stt out from under a still-live loop.
Switch to asyncio.TaskGroup so a failing loop cancels+awaits the siblings
before teardown. Add a regression test asserting an error in the conversation
loop cancels the perception loop and still closes every source.
Make source/vision optional so the conversation loop runs with no screen
capture. Add Settings.voice() preset and `python -m wsai --voice` demo.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Modular async pipeline: FrameSource->Vision->context and STT/text->Brain->TTS.
All stages are Protocols; mock backends run end-to-end with no deps/keys.
Real backends included: mss screen capture, Claude vision+brain (guarded imports).
