feat: condition node functionality with CEL evaluation in Workflows (#2280)

* feat: add condition node functionality with CEL evaluation

- Introduced ConditionNode to support conditional branching in workflows.
- Implemented CEL evaluation for state updates and condition expressions.
- Updated WorkflowEngine to handle condition nodes and their execution logic.
- Enhanced validation for workflows to ensure condition nodes have at least two outgoing edges and valid expressions.
- Modified frontend components to support new condition node type and its configuration.
- Added necessary types and interfaces for condition cases and state operations.
- Updated requirements to include cel-python for expression evaluation.

* mini-fixes

* feat(workflow): improve UX

---------

Co-authored-by: Alex <a@tushynski.me>

application/agents/workflows/cel_evaluator.py

@@ -0,0 +1,64 @@
+from typing import Any, Dict
+
+import celpy
+import celpy.celtypes
+
+
+class CelEvaluationError(Exception):
+    pass
+
+
+def _convert_value(value: Any) -> Any:
+    if isinstance(value, bool):
+        return celpy.celtypes.BoolType(value)
+    if isinstance(value, int):
+        return celpy.celtypes.IntType(value)
+    if isinstance(value, float):
+        return celpy.celtypes.DoubleType(value)
+    if isinstance(value, str):
+        return celpy.celtypes.StringType(value)
+    if isinstance(value, list):
+        return celpy.celtypes.ListType([_convert_value(item) for item in value])
+    if isinstance(value, dict):
+        return celpy.celtypes.MapType(
+            {celpy.celtypes.StringType(k): _convert_value(v) for k, v in value.items()}
+        )
+    if value is None:
+        return celpy.celtypes.BoolType(False)
+    return celpy.celtypes.StringType(str(value))
+
+
+def build_activation(state: Dict[str, Any]) -> Dict[str, Any]:
+    return {k: _convert_value(v) for k, v in state.items()}
+
+
+def evaluate_cel(expression: str, state: Dict[str, Any]) -> Any:
+    if not expression or not expression.strip():
+        raise CelEvaluationError("Empty expression")
+    try:
+        env = celpy.Environment()
+        ast = env.compile(expression)
+        program = env.program(ast)
+        activation = build_activation(state)
+        result = program.evaluate(activation)
+    except celpy.CELEvalError as exc:
+        raise CelEvaluationError(f"CEL evaluation error: {exc}") from exc
+    except Exception as exc:
+        raise CelEvaluationError(f"CEL error: {exc}") from exc
+    return cel_to_python(result)
+
+
+def cel_to_python(value: Any) -> Any:
+    if isinstance(value, celpy.celtypes.BoolType):
+        return bool(value)
+    if isinstance(value, celpy.celtypes.IntType):
+        return int(value)
+    if isinstance(value, celpy.celtypes.DoubleType):
+        return float(value)
+    if isinstance(value, celpy.celtypes.StringType):
+        return str(value)
+    if isinstance(value, celpy.celtypes.ListType):
+        return [cel_to_python(item) for item in value]
+    if isinstance(value, celpy.celtypes.MapType):
+        return {str(k): cel_to_python(v) for k, v in value.items()}
+    return value