Add execution engine and task lifecycle services

tests/unit/test_execution_engine.py

@@ -0,0 +1,47 @@
+from ai_orchestrator.application.services.execution import (
+    DefaultFinalizer,
+    FinalizerNodeRunner,
+    GraphExecutionEngine,
+    NoOpReviewer,
+    PlannerNodeRunner,
+    RunnerRegistry,
+)
+from ai_orchestrator.domain.enums import NodeStatus, NodeType, TaskStatus
+from ai_orchestrator.domain.models import ExecutionGraph, ExecutionNode, Task
+from ai_orchestrator.infrastructure.storage.memory import InMemoryEventStore
+
+
+def test_execution_engine_runs_ready_nodes_and_records_events() -> None:
+    task = Task(project_id="default", goal="Run planner", inputs={})
+    planner = ExecutionNode(task_id=task.task_id, node_type=NodeType.PLANNER, input_data={})
+    finalizer = ExecutionNode(
+        task_id=task.task_id,
+        node_type=NodeType.FINALIZER,
+        input_data={},
+        dependencies=[planner.node_id],
+    )
+    graph = ExecutionGraph(task_id=task.task_id, nodes=[planner, finalizer])
+    event_store = InMemoryEventStore()
+    registry = RunnerRegistry()
+    registry.register(PlannerNodeRunner())
+    registry.register(FinalizerNodeRunner(finalizer=DefaultFinalizer()))
+    engine = GraphExecutionEngine(
+        event_store=event_store,
+        runner_registry=registry,
+        reviewer=NoOpReviewer(),
+    )
+
+    first_pass = engine.execute_ready_nodes(task=task, graph=graph)
+    second_pass = engine.execute_ready_nodes(task=task, graph=graph)
+
+    assert len(first_pass) == 1
+    assert len(second_pass) == 1
+    assert planner.status == NodeStatus.COMPLETED
+    assert finalizer.status == NodeStatus.COMPLETED
+    assert task.status == TaskStatus.RUNNING
+    assert [event.event_type for event in event_store.items] == [
+        "node_started",
+        "node_completed",
+        "node_started",
+        "node_completed",
+    ]