feat(core/agent): 添加 Step 和 LoopResult 数据类

保真 TRM4 算法 #11，Step 新增 call_id 字段。

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/unit/test_agent_types.py

@@ -0,0 +1,50 @@
+"""core/agent/types.py 单元测试。"""
+from __future__ import annotations
+
+from core.agent.types import LoopResult, Step
+
+
+class TestStep:
+    def test_creation(self) -> None:
+        step = Step(
+            thought="thinking...",
+            reflect={"key": "value"},
+            plan={"next": "do something"},
+            tool_call={"tool": "search", "args": {"query": "test"}},
+            tool_output="result text",
+            raw_content='{"reflect": {}, "plan": {}, "action": {}}',
+            call_id="uuid-1",
+        )
+        assert step.thought == "thinking..."
+        assert step.tool_call["tool"] == "search"
+        assert step.call_id == "uuid-1"
+
+
+class TestLoopResult:
+    def test_defaults(self) -> None:
+        lr = LoopResult()
+        assert lr.result is None
+        assert lr.steps == []
+        assert lr.steps_used == 0
+        assert lr.token_usage == {"prompt_tokens": 0, "completion_tokens": 0}
+        assert lr.stop_reason == "finished"
+
+    def test_with_steps(self) -> None:
+        step = Step(
+            thought="t", reflect={}, plan={},
+            tool_call={"tool": "t", "args": {}},
+            tool_output="o", raw_content="r", call_id="c",
+        )
+        lr = LoopResult(
+            result={"answer": "42"}, steps=[step], steps_used=1,
+            token_usage={"prompt_tokens": 100, "completion_tokens": 50},
+            stop_reason="finished",
+        )
+        assert lr.result == {"answer": "42"}
+        assert len(lr.steps) == 1
+
+    def test_separate_instances_have_independent_lists(self) -> None:
+        lr1 = LoopResult()
+        lr2 = LoopResult()
+        lr1.steps.append(Step("t", {}, {}, {"tool": "x", "args": {}}, "o", "r", "c"))
+        assert len(lr2.steps) == 0