feat: adiciona Silero VAD local com configuração por ambiente

README.md

@@ -390,7 +390,7 @@ src/voice_assistant/
   audio_gateway/app/            WebSocket endpoint and protocol
   application/                  VoiceSession and transport-independent events
   domain/                       Session state and domain rules
-  vad/                          VAD port and speech boundaries; runtime integration pending
+  vad/                          VAD port, speech boundaries, and local Silero adapter
   audio/                        Canonical audio models
   stt/                          STT contract, mock and NVIDIA adapter
   agent/                        Agent contract and mock adapter
@@ -432,5 +432,70 @@ boundary. Model padding never extends the input timeline.
 `reset()` discards detection state and restarts the timeline, and `aclose()`
 releases resources without emitting new speech events. Calls are serialized.
 These contracts do not start turns, select providers, or carry transport IDs.
-The Silero implementation, application integration, and browser VAD replacement
-are subsequent tasks. This step leaves the active conversation flow unchanged.
+The local Silero implementation is available independently of the running
+conversation. Application integration and browser VAD replacement are subsequent
+tasks; the active conversation flow still uses its existing browser VAD.
+
+
+### Local Silero VAD adapter
+
+`vad/silero.py` implements `VADAdapter` with the official Silero model and
+`VADIterator`. `silero-vad[onnx-cpu]==6.2.3` bundles the model files; model loading
+and inference use CPU locally, without runtime downloads or `torch.hub`.
+The upstream package also requires PyTorch. The uv source configuration selects
+CPU builds on Linux/Windows and the standard PyPI build on macOS.
+
+Each adapter owns its model state, PCM buffer, and input timeline. It converts
+PCM S16LE to normalized float samples, buffers 512-sample windows, and maps
+Silero boundaries to the application events. Defaults are threshold 0.5,
+300 ms of silence, 30 ms speech padding, and a 10-second worker wait limit.
+These values are initial settings, to be tuned with real conversational audio.
+
+`process()` may return several events for a large chunk. `flush()` pads a final
+partial window internally while keeping event positions within real audio.
+`reset()` discards detection state and restarts the timeline. `aclose()` discards
+pending input and releases model references without emitting speech events.
+
+Model loading and inference run outside the event loop. Cancellation or a worker
+timeout requires reset before accepting more audio. Outstanding workers retain
+ownership: reset/close wait for them, with bounded waits and retry on timeout.
+Running native inference is not forcibly terminated by coroutine cancellation.
+
+Tests with a controlled iterator cover framing, positions, isolation, and worker
+ownership. `tests/test_silero_vad_integration.py` exercises the installed ONNX
+model with network access blocked; it skips when the Silero dependency is absent.
+It can be run with:
+
+```bash
+uv run pytest -q tests/test_silero_vad.py tests/test_silero_vad_integration.py
+```
+
+Upstream source and license: [Silero VAD](https://github.com/snakers4/silero-vad)
+([MIT](https://github.com/snakers4/silero-vad/blob/master/LICENSE)).
+
+
+### VAD configuration by environment
+
+The active environment YAML configures VAD using the same `provider`/`options`
+structure as STT, Agent, and TTS. `config/development.yaml` contains:
+
+```yaml
+vad:
+  provider: silero
+  options:
+    threshold: 0.5
+    min_silence_duration_ms: 300
+    speech_pad_ms: 30
+    worker_timeout_seconds: 10.0
+```
+
+`APP_ENV` selects the environment through the existing configuration loader.
+`create_vad_adapter(config, catalog)` resolves the VAD from `config/providers.yaml`
+and passes the environment options to its constructor. The Silero constructor
+retains defaults for direct use and missing options. A missing `vad` section
+remains compatible with existing configurations; explicitly creating VAD in
+such an environment raises a configuration error. Changing YAML values affects
+new adapter instances after configuration is reloaded; there is no live reload.
+
+This factory makes the configuration usable independently. Connecting it to the
+conversation lifecycle remains the next task.