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/pipeline/asr_flow.py

@@ -0,0 +1,13 @@
+"""ASR flow helpers extracted from the duplex pipeline.
+
+This module is intentionally lightweight for phase-wise migration.
+"""
+
+from __future__ import annotations
+
+from providers.common.base import ASRResult
+
+
+def is_final_result(result: ASRResult) -> bool:
+    """Return whether an ASR result is final."""
+    return bool(result.is_final)