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/session/lifecycle.py

@@ -0,0 +1,10 @@
+"""Lifecycle helper utilities for runtime sessions."""
+
+from __future__ import annotations
+
+from datetime import datetime, timezone
+
+
+def utc_now_iso() -> str:
+    """Return current UTC timestamp in ISO 8601 format."""
+    return datetime.now(timezone.utc).isoformat()