feat: 重写沙箱 + 完整测试套件 (192 tests)

沙箱 v2 - 多层隔离:
- AST 静态分析: 30+ 危险模式检测
- 子进程隔离: 独立进程执行 + 资源限制
- 网络阻断: socket 模块替换
- 模块白名单: 30 个安全模块
- 文件系统限制: 临时目录隔离
- SandboxResult 数据类 + 执行历史

测试套件 (8 个模块, 192 个用例):
- test_sandbox.py:     AST检查(47) + 沙箱执行(15) + 安全拒绝(20) + 超时(2) + 模式对比(3)
- test_conversation.py: 响应解析(13) + 思考标记(5) + 工具提取(10)
- test_config.py:       配置加载/保存/缓存/损坏处理(8)
- test_history.py:      历史CRUD/持久化/边界(12)
- test_engines.py:      引擎管理/加载/切换(14)
- test_plugins.py:      code_editor(10) + code_search(7) + git_tools(4) + tool_manager(7)
- test_integration.py:  沙箱+对话(2) + 历史+对话(2) + 安全链(3) + 提示词(1)

tests/test_history.py

@@ -0,0 +1,114 @@
+"""对话历史管理测试"""
+import os
+import sys
+import json
+import pytest
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+from xiaoli.conversation.history import History
+
+
+class TestHistory:
+    """History 类测试"""
+
+    def test_add_message(self, history_dir):
+        h = History(history_dir)
+        h.add("user", "hello")
+        h.add("assistant", "hi there")
+        assert len(h.messages) == 2
+        assert h.messages[0] == {"role": "user", "content": "hello"}
+        assert h.messages[1] == {"role": "assistant", "content": "hi there"}
+
+    def test_get_messages(self, history_dir):
+        h = History(history_dir)
+        h.add("user", "q1")
+        h.add("assistant", "a1")
+        msgs = h.get()
+        assert len(msgs) == 2
+        assert msgs[0]['role'] == 'user'
+
+    def test_clear(self, history_dir):
+        h = History(history_dir)
+        h.add("user", "hello")
+        h.add("assistant", "hi")
+        h.clear()
+        assert len(h.messages) == 0
+
+    def test_max_items(self, history_dir):
+        h = History(history_dir, max_items=3)
+        for i in range(5):
+            h.add("user", f"msg {i}")
+        assert len(h.messages) == 3
+        assert h.messages[0]['content'] == 'msg 2'
+
+    def test_save_and_load(self, history_dir):
+        h = History(history_dir)
+        h.add("user", "hello")
+        h.add("assistant", "hi")
+        assert h.save("test_chat")
+
+        h2 = History(history_dir)
+        assert h2.load("test_chat")
+        assert len(h2.messages) == 2
+        assert h2.messages[0]['content'] == 'hello'
+
+    def test_load_nonexistent(self, history_dir, capsys):
+        h = History(history_dir)
+        result = h.load("nonexistent_chat")
+        assert not result
+
+    def test_list_saved(self, history_dir, capsys):
+        h = History(history_dir)
+        h.add("user", "test")
+        h.save("chat1")
+        h.save("chat2")
+
+        h2 = History(history_dir)
+        h2.list_saved()  # should not raise
+        captured = capsys.readouterr()
+        assert 'chat1' in captured.out or 'chat2' in captured.out
+
+    def test_list_saved_empty(self, history_dir, capsys):
+        h = History(history_dir)
+        h.list_saved()
+        captured = capsys.readouterr()
+        assert 'no' in captured.out.lower() or '没有' in captured.out
+
+    def test_set_all(self, history_dir):
+        h = History(history_dir)
+        msgs = [
+            {"role": "user", "content": "q"},
+            {"role": "assistant", "content": "a"},
+        ]
+        h.set_all(msgs)
+        assert len(h.messages) == 2
+        assert h.messages == msgs
+
+    def test_save_creates_directory(self, tmp_dir):
+        nested_dir = os.path.join(tmp_dir, "deep", "nested", "history")
+        h = History(nested_dir)
+        h.add("user", "test")
+        h.save("test")
+        assert os.path.exists(os.path.join(nested_dir, "test.json"))
+
+    def test_save_file_format(self, history_dir):
+        h = History(history_dir)
+        h.add("user", "hello")
+        h.save("format_test")
+
+        path = os.path.join(history_dir, "format_test.json")
+        with open(path, 'r') as f:
+            data = json.load(f)
+        assert 'timestamp' in data
+        assert 'conversation' in data
+        assert len(data['conversation']) == 1
+
+    def test_load_corrupted_file(self, history_dir):
+        path = os.path.join(history_dir, "corrupt.json")
+        with open(path, 'w') as f:
+            f.write("{bad json")
+
+        h = History(history_dir)
+        result = h.load("corrupt")
+        assert not result