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/events_out.py

@@ -0,0 +1,12 @@
+"""Output-event shaping helpers for the runtime pipeline."""
+
+from __future__ import annotations
+
+from typing import Any, Dict
+
+
+def assistant_text_delta_event(text: str, **extra: Any) -> Dict[str, Any]:
+    """Build a normalized assistant text delta payload."""
+    payload: Dict[str, Any] = {"type": "assistant.text.delta", "text": str(text)}
+    payload.update(extra)
+    return payload