feat: 添加角色事件评论系统

- 新增 Opinion 模型，记录角色对事件的观点
- 新增 opinions.py，基于规则生成观点（支持5种事件×3种情绪）
- 同一事件生命周期内每个 agent 只生成一次观点
- 观点同时记录到 agent.memory
- 新增 3 个测试用例

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

engine-python/tests/test_step.py

@@ -171,3 +171,61 @@ def test_global_event_cooldown(client):
     assert data["global_event"]["triggered"] is False
     # 冷却递减
     assert data["world_state"]["global_meter"]["cooldown"] == 4
+
+
+def test_opinion_generated_on_world_effect(client):
+    """测试世界事件触发时生成观点"""
+    # 触发世界事件
+    events = [
+        {"type": "chaos", "text": f"chaos{i}", "user": "test", "ts": i}
+        for i in range(20)
+    ]
+    resp = client.post("/step", json={"events": events})
+    data = resp.json()
+
+    # 验证事件触发
+    assert data["global_event"]["triggered"] is True
+    assert len(data["world_state"]["world_effects"]) > 0
+
+    # 验证每个 agent 都有 opinion
+    for agent_id, agent in data["world_state"]["agents"].items():
+        assert agent["opinion"] is not None
+        assert "about" in agent["opinion"]
+        assert "text" in agent["opinion"]
+        assert "tick" in agent["opinion"]
+
+
+def test_opinion_only_once_per_effect(client):
+    """测试同一事件只生成一次观点"""
+    # 触发世界事件
+    events = [
+        {"type": "chaos", "text": f"chaos{i}", "user": "test", "ts": i}
+        for i in range(20)
+    ]
+    resp = client.post("/step", json={"events": events})
+    data = resp.json()
+
+    # 记录第一次的观点
+    first_opinions = {
+        aid: agent["opinion"]["text"]
+        for aid, agent in data["world_state"]["agents"].items()
+    }
+
+    # 再次调用 step（事件仍在持续）
+    resp2 = client.post("/step", json={"events": []})
+    data2 = resp2.json()
+
+    # 观点应该保持不变（不重新生成）
+    for aid, agent in data2["world_state"]["agents"].items():
+        if agent["opinion"]:
+            assert agent["opinion"]["text"] == first_opinions[aid]
+
+
+def test_opinion_cleared_when_no_effect(client):
+    """测试无活跃事件时观点为空"""
+    resp = client.post("/step", json={"events": []})
+    data = resp.json()
+
+    # 无世界事件时，opinion 应为 None
+    for agent_id, agent in data["world_state"]["agents"].items():
+        assert agent["opinion"] is None