feat: opencode 式会话持久化 + /resume 一键恢复

此前只有手动的 /chat save|list|open，关终端就丢上下文。现升级为
opencode 式体验：每轮对话自动落盘、启动提示历史会话、/resume 一键恢复。

- 新增 xcli_core/session.py：Session 数据类（id/title/created_at/updated_at/
  engine/model/messages）+ SessionManager（new/save/list/load/resolve，存
  chat_history/<id>.json）。向后兼容旧 /chat 格式（无 id、用 conversation 键，
  读取时回退用文件名作 id）。标题自动取首条 user 消息前若干字。
- HistoryMixin 升级（cli_history.py）：新增 init_session_manager /
  _autosave_session / handle_resume_command。自动保存首轮惰性建会话、
  更新标题与 updated_at；/resume 列出(序号|ID)或按序号|ID|前缀恢复，
  恢复时把 messages 载入 shared_conversation_history 并同步引擎。
- 集成：cli_base.__init__ 在 chat_history_dir 就绪后 init_session_manager；
  cli_core 主循环 1395 行 process_conversation 后调用 _autosave_session；
  新增 /resume|/sessions 路由（/sessions 等同 /resume）。
- 体验：启动时若有历史会话提示 /resume（含最近会话标题）；run() 紧凑提示
  与 /help 速查表均补 /resume（列出/恢复/开新会话）。
- 修复 cli_history.py 一处历史 typo：{Style.RESET型} -> {Style.RESET_ALL}
  （旧 load_chat_history 在含消息时会抛 AttributeError）。
- 测试：新增 tests/test_session.py（12 项，覆盖兼容/新建/落盘/排序/解析/
  自动保存/恢复/列表/未知token，全程临时目录不污染真实 config/chat_history）。
  全量 242 passed（原 230）。

真实 CLI 冒烟：启动提示识别到历史会话、/resume 正确列出（含标题/时间/引擎/
条数）、/resume <id> 正确恢复并回显；已清理测试种入文件，chat_history 复原为空。

tests/test_session.py

@@ -0,0 +1,187 @@
+"""会话持久化与 /resume 的回归测试。
+
+全程使用临时目录，不触碰真实 chat_history/ 与 config.json。
+"""
+import os
+import json
+import tempfile
+import shutil
+import uuid
+
+import pytest
+
+from xcli_core.session import Session, SessionManager, _make_session_id, _title_from_messages
+
+
+@pytest.fixture
+def tmp_history():
+    d = tempfile.mkdtemp(prefix="xiaoli_sess_")
+    yield d
+    shutil.rmtree(d, ignore_errors=True)
+
+
+def _write_old_format(history_dir, name, messages):
+    """模拟旧 /chat save 写入（无 id 字段、用 conversation 键）。"""
+    path = os.path.join(history_dir, f"{name}.json")
+    with open(path, "w", encoding="utf-8") as f:
+        json.dump({"timestamp": "2026-08-01 10:00:00", "conversation": messages}, f, ensure_ascii=False)
+    return path
+
+
+# ── SessionManager 单元 ──
+
+def test_session_id_format():
+    sid = _make_session_id()
+    assert len(sid.split("-")) == 3  # YYYYMMDD-HHMMSS-xxxxxx
+
+
+def test_new_session_basic_fields(tmp_history):
+    mgr = SessionManager(tmp_history)
+    s = mgr.new_session(engine="openai", model="xophunyuan7bmt")
+    assert s.id and s.engine == "openai" and s.model == "xophunyuan7bmt"
+    assert s.messages == [] and s.title == "(新会话)"
+
+
+def test_save_then_load_roundtrip(tmp_history):
+    mgr = SessionManager(tmp_history)
+    s = mgr.new_session(engine="openai", model="gpt-4o")
+    msgs = [{"role": "user", "content": "你好"}, {"role": "assistant", "content": "你也好"}]
+    assert mgr.save(s, msgs, engine="openai", model="gpt-4o") is True
+    loaded = mgr.load(s.id)
+    assert loaded is not None
+    assert loaded.msg_count == 2
+    assert loaded.messages[0]["content"] == "你好"
+    assert loaded.engine == "openai" and loaded.model == "gpt-4o"
+
+
+def test_title_generated_from_first_user_msg(tmp_history):
+    mgr = SessionManager(tmp_history)
+    s = mgr.new_session()
+    msgs = [{"role": "user", "content": "帮我写一个快排函数"}]
+    mgr.save(s, msgs)
+    loaded = mgr.load(s.id)
+    assert "快排" in loaded.title
+
+
+def test_list_sessions_sorted_desc(tmp_history):
+    mgr = SessionManager(tmp_history)
+    # 写入两个会话，并强制 s1 的更新时间更早，制造稳定可排序差
+    s1 = mgr.new_session(); mgr.save(s1, [{"role": "user", "content": "旧会话A"}])
+    path1 = os.path.join(tmp_history, f"{s1.id}.json")
+    with open(path1, "r", encoding="utf-8") as f:
+        d = json.load(f)
+    d["updated_at"] = "2020-01-01 00:00:00"
+    with open(path1, "w", encoding="utf-8") as f:
+        json.dump(d, f, ensure_ascii=False)
+    s2 = mgr.new_session(); mgr.save(s2, [{"role": "user", "content": "新会话B"}])
+    sessions = mgr.list_sessions()
+    assert len(sessions) == 2
+    # 倒序：更新的在前（updated_at 时间戳更大）
+    assert sessions[0].id == s2.id
+
+
+def test_resolve_by_index_and_prefix(tmp_history):
+    mgr = SessionManager(tmp_history)
+    s1 = mgr.new_session(); mgr.save(s1, [{"role": "user", "content": "x"}])
+    s2 = mgr.new_session(); mgr.save(s2, [{"role": "user", "content": "y"}])
+    sessions = mgr.list_sessions()
+    by_idx = mgr.resolve("1", sessions)
+    by_id = mgr.resolve(s2.id, sessions)
+    by_prefix = mgr.resolve(s2.id[:20], sessions)
+    assert by_idx is not None and by_idx.id == sessions[0].id
+    assert by_id is not None and by_id.id == s2.id
+    assert by_prefix is not None and by_prefix.id == s2.id
+
+
+def test_compat_old_chat_format(tmp_history):
+    """兼容旧 /chat save 写入的文件（无 id、conversation 键）。"""
+    _write_old_format(tmp_history, "我的旧记录",
+                      [{"role": "user", "content": "旧消息"}])
+    mgr = SessionManager(tmp_history)
+    sessions = mgr.list_sessions()
+    assert len(sessions) == 1
+    s = sessions[0]
+    assert s.id == "我的旧记录"  # 回退用文件名
+    assert s.msg_count == 1
+    assert s.messages[0]["content"] == "旧消息"
+
+
+# ── 与 CLI 集成（用 stub 复用 HistoryMixin 的会话方法） ──
+
+from xcli_core.cli_history import HistoryMixin as HistoryMixinStubBase
+
+
+class _Stub(HistoryMixinStubBase):
+    def __init__(self, history_dir):
+        self.chat_history_dir = history_dir
+        self.shared_conversation_history = []
+        self.current_session = None
+        self.current_engine = None
+        self.current_model = None
+        self.session_manager = SessionManager(history_dir)
+
+    def _set_shared_conversation_history(self):
+        # 真实 AICLI 会把列表同步给所有引擎，这里做成空操作
+        pass
+
+
+def test_autosave_creates_session_lazily(tmp_history):
+    stub = _Stub(tmp_history)
+    stub.shared_conversation_history = [{"role": "user", "content": "首条"}]
+    stub._autosave_session()
+    assert stub.current_session is not None
+    sessions = stub.session_manager.list_sessions()
+    assert len(sessions) == 1
+    assert sessions[0].msg_count == 1
+
+
+def test_autosave_updates_existing_session(tmp_history):
+    stub = _Stub(tmp_history)
+    stub.shared_conversation_history = [{"role": "user", "content": "a"}]
+    stub._autosave_session()  # 建
+    stub.shared_conversation_history.append({"role": "assistant", "content": "b"})
+    stub._autosave_session()  # 更新
+    sessions = stub.session_manager.list_sessions()
+    assert len(sessions) == 1
+    assert sessions[0].msg_count == 2
+
+
+def test_handle_resume_lists_and_restores(tmp_history, capsys):
+    stub = _Stub(tmp_history)
+    # 先写一个会话
+    stub.shared_conversation_history = [{"role": "user", "content": "历史问题"}]
+    stub._autosave_session()
+    first_id = stub.current_session.id
+
+    # 清空当前上下文，模拟新会话
+    stub.shared_conversation_history = []
+    stub.current_session = None
+
+    # /resume 列出
+    stub.handle_resume_command("")
+    out = capsys.readouterr().out
+    assert "已保存的会话" in out
+
+    # /resume <id> 恢复
+    stub.handle_resume_command(first_id)
+    assert stub.shared_conversation_history == [{"role": "user", "content": "历史问题"}]
+    assert stub.current_session.id == first_id
+
+
+def test_handle_resume_new_clears_current(tmp_history):
+    stub = _Stub(tmp_history)
+    stub.shared_conversation_history = [{"role": "user", "content": "x"}]
+    stub._autosave_session()
+    assert stub.current_session is not None
+    stub.handle_resume_command("new")
+    assert stub.current_session is None
+
+
+def test_handle_resume_unknown_token(tmp_history, capsys):
+    stub = _Stub(tmp_history)
+    # 先写一个会话，使目录非空，才能走到「未找到」分支而非「没有可恢复」
+    stub.shared_conversation_history = [{"role": "user", "content": "历史"}]
+    stub._autosave_session()
+    stub.handle_resume_command("nonexistent-id")
+    out = capsys.readouterr().out
+    assert "未找到会话" in out