Refactor project structure and enhance backend integration

- Expanded package inclusion in `pyproject.toml` to support new modules.
- Introduced new `adapters` and `protocol` packages for better organization.
- Added backend adapter implementations for control plane integration.
- Updated main application imports to reflect new package structure.
- Removed deprecated core components and adjusted documentation accordingly.
- Enhanced architecture documentation to clarify the new runtime and integration layers.

engine/runtime/ports/asr.py

@@ -0,0 +1,64 @@
+"""ASR extension port contracts."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import AsyncIterator, Awaitable, Callable, Optional, Protocol
+
+from providers.common.base import ASRResult
+
+TranscriptCallback = Callable[[str, bool], Awaitable[None]]
+
+
+@dataclass(frozen=True)
+class ASRServiceSpec:
+    """Resolved runtime configuration for ASR service creation."""
+
+    provider: str
+    sample_rate: int
+    language: str = "auto"
+    api_key: Optional[str] = None
+    api_url: Optional[str] = None
+    model: Optional[str] = None
+    interim_interval_ms: int = 500
+    min_audio_for_interim_ms: int = 300
+    on_transcript: Optional[TranscriptCallback] = None
+
+
+class ASRPort(Protocol):
+    """Port for speech recognition providers."""
+
+    async def connect(self) -> None:
+        """Establish connection to ASR provider."""
+
+    async def disconnect(self) -> None:
+        """Release ASR resources."""
+
+    async def send_audio(self, audio: bytes) -> None:
+        """Push one PCM audio chunk for recognition."""
+
+    async def receive_transcripts(self) -> AsyncIterator[ASRResult]:
+        """Stream partial/final recognition results."""
+
+
+class ASRInterimControl(Protocol):
+    """Optional extension for explicit interim transcription control."""
+
+    async def start_interim_transcription(self) -> None:
+        """Start interim transcription loop if supported."""
+
+    async def stop_interim_transcription(self) -> None:
+        """Stop interim transcription loop if supported."""
+
+
+class ASRBufferControl(Protocol):
+    """Optional extension for explicit ASR buffer lifecycle control."""
+
+    def clear_buffer(self) -> None:
+        """Clear provider-side ASR buffer."""
+
+    async def get_final_transcription(self) -> str:
+        """Return final transcription for the current utterance."""
+
+    def get_and_clear_text(self) -> str:
+        """Return buffered text and clear internal state."""