feat: integra VAD ao controle de turnos da conversa

README.md

@@ -388,7 +388,7 @@ The script reads `audios/chafik_normalize.wav` (16 kHz, mono, 16-bit PCM), sends
 config/                         Environment YAML and provider catalog
 src/voice_assistant/
   audio_gateway/app/            WebSocket endpoint and protocol
-  application/                  VoiceSession and transport-independent events
+  application/                  VoiceSession, continuous PCM history, and application events
   domain/                       Session state and domain rules
   vad/                          VAD port, speech boundaries, and local Silero adapter
   audio/                        Canonical audio models
@@ -418,7 +418,7 @@ tools/                          Integration and smoke scripts
 
 
 
-## Backend VAD contract (integration pending)
+## Backend VAD contract
 
 `vad/adapter.py` defines one stateful detector per continuous input stream.
 Its input is the canonical PCM S16LE, mono, 16 kHz audio format. Arbitrary
@@ -432,9 +432,9 @@ 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 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.
+The Silero adapter can control turns through the continuous VoiceSession API.
+Browser/WebSocket migration is the next task; the existing web client continues
+to use its current turn commands until that migration.
 
 
 ### Local Silero VAD adapter
@@ -497,5 +497,49 @@ 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.
+The VAD factory can be supplied to continuous voice sessions. The existing web
+client remains on manual turn commands until the browser migration.
+
+
+### Continuous audio and backend turn control
+
+A `VoiceSession` constructed with a VAD receives continuous canonical PCM through
+`await session.receive_audio(pcm)`. The caller supplies audio without a turn ID;
+the channel owns transport sequencing. `SpeechStarted` opens an STT turn and
+`SpeechEnded` schedules normal STT finalization in the background. New speech
+interrupts an active response/finalization before opening a fresh turn. Empty
+STT results release the turn through an interruption event rather than leaving
+an active turn behind. The VAD is not reset between conversation turns.
+
+The application's sample-indexed audio history preserves the beginning of speech
+when VAD confirmation arrives later. PCM already sent to a turn is not replayed
+within that turn; pre-roll never includes the previous utterance. History and
+input size are bounded by environment configuration:
+
+```yaml
+voice_input:
+  pre_roll_ms: 200
+  history_ms: 2000
+  max_input_chunk_bytes: 65536
+```
+
+History is trimmed after processing each input chunk; transient storage is at most
+retained history plus one accepted chunk. A speech start older than retained
+history is reported as an input error instead of silently dropping speech.
+Invalid PCM is rejected before detection or timeline advancement. A processing
+failure requires a new session; cleanup still releases VAD and provider resources.
+
+Use `finish_audio_input()` for normal end of a continuous stream. Session end or
+disconnect aborts through `end()`/`aclose()`, without forcing a final speech event.
+The caller shields cleanup from transport cancellation, as for manual sessions.
+
+Backend-controlled sessions emit `TurnOpened` and `TurnInterrupted`; the WebSocket
+mapper translates them to the existing `turn.started` and `interrupted` events.
+Adapters should discard outdated queued playback when a new turn opens: backend
+turn completion describes produced output, not physical speaker completion.
+
+Manual `start_turn`/`send_audio`/`stop_turn` commands remain available on sessions
+without VAD. Mixing those commands with a VAD-controlled session is rejected.
+`create_voice_session(..., server_vad=True)` composes the continuous backend API;
+the current `/ws/audio` receive loop still uses the manual mode. The next task
+connects continuous input to that route and simplifies the browser accordingly.