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/__init__.py

@@ -0,0 +1 @@
+"""Runtime session package."""

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()

engine/runtime/session/metadata.py

@@ -0,0 +1,9 @@
+"""Metadata helpers extracted from session manager."""
+
+from __future__ import annotations
+
+import re
+from typing import Pattern
+
+DYNAMIC_VARIABLE_KEY_RE: Pattern[str] = re.compile(r"^[a-zA-Z_][a-zA-Z0-9_]{0,63}$")
+DYNAMIC_VARIABLE_PLACEHOLDER_RE: Pattern[str] = re.compile(r"\{\{\s*([a-zA-Z_][a-zA-Z0-9_]*)\s*\}\}")

engine/runtime/session/workflow_bridge.py

@@ -0,0 +1,12 @@
+"""Workflow bridge helpers for runtime session orchestration."""
+
+from __future__ import annotations
+
+from typing import Optional
+
+from workflow.runner import WorkflowRunner
+
+
+def has_active_workflow(workflow_runner: Optional[WorkflowRunner]) -> bool:
+    """Return whether a workflow runner exists and has a current node."""
+    return bool(workflow_runner and workflow_runner.current_node is not None)