feat(server): 会话上下文保留（LLM 历史 + 确定性兜底双保险）

解决用户删除草稿后说'再提交'丢失上下文的问题：

- steward.py 新增 _inject_recent_conversation_history：build_plan 前读最近 10 条对话注入 context_json
- steward_intent_agent.py 的 _build_messages 把 recent_history 暴露给模型，system prompt 加确认类话术引导
- 新建 steward_context_resume.py：should_resume_recent_task 检测'再提交'类话术 + state 有可恢复 flow，attach_resumed_task 从 state 恢复 task
- 两个 plan 入口（/plans 和 /plans/stream）都已接入双保险
- 后端 67 passed，端到端验证'上海出差→再提交'成功恢复 task

server/tests/test_steward_context_resume.py

@@ -0,0 +1,130 @@
+from __future__ import annotations
+
+from datetime import date
+
+from app.schemas.steward import StewardPlanResponse, StewardTask, StewardThinkingEvent
+from app.services.steward_context_resume import (
+    RESUME_CONFIRMATION_KEYWORDS,
+    attach_resumed_task,
+    resume_task_from_flow,
+    should_resume_recent_task,
+)
+
+
+def _state_with_travel_application(fields: dict | None = None) -> dict:
+    return {
+        "active_flow": "travel_application",
+        "flows": {
+            "travel_application": {
+                "flow_id": "travel_application",
+                "status": "ready_for_confirmation",
+                "fields": fields or {"location": "上海", "time_range": "2026-02-20 至 2026-02-23"},
+                "missing_fields": [],
+            }
+        },
+    }
+
+
+def test_should_resume_returns_flow_id_for_confirmation_keyword_with_state():
+    state = _state_with_travel_application()
+    for keyword in ("再提交", "继续提交", "重新提交", "再申请", "重新申请", "那就提交", "继续吧", "再试一次"):
+        assert should_resume_recent_task(keyword, state) == "travel_application", f"keyword={keyword}"
+
+
+def test_should_resume_returns_none_when_state_empty():
+    assert should_resume_recent_task("再提交", {}) is None
+    assert should_resume_recent_task("再提交", None) is None
+
+
+def test_should_resume_returns_none_for_non_confirmation_message():
+    state = _state_with_travel_application()
+    assert should_resume_recent_task("今天天气不错", state) is None
+    assert should_resume_recent_task("你好", state) is None
+    assert should_resume_recent_task("查一下差旅标准", state) is None
+    assert should_resume_recent_task("", state) is None
+
+
+def test_should_resume_returns_none_when_flow_has_no_fields():
+    state = {
+        "active_flow": "travel_application",
+        "flows": {"travel_application": {"fields": {}, "missing_fields": []}},
+    }
+    assert should_resume_recent_task("再提交", state) is None
+
+
+def test_should_resume_finds_flow_when_active_flow_empty():
+    # active_flow 已清空，但 flows 里仍有可恢复的 flow
+    state = {
+        "active_flow": "",
+        "flows": {
+            "travel_application": {
+                "fields": {"location": "武汉"},
+            }
+        },
+    }
+    assert should_resume_recent_task("再提交", state) == "travel_application"
+
+
+def test_resume_task_from_flow_restores_travel_application():
+    flow = {
+        "flow_id": "travel_application",
+        "fields": {"location": "上海", "time_range": "2026-02-20 至 2026-02-23"},
+        "missing_fields": [],
+    }
+    task = resume_task_from_flow("travel_application", flow, task_index=1)
+    assert task.task_type == "expense_application"
+    assert task.assigned_agent == "application_assistant"
+    assert task.ontology_fields["location"] == "上海"
+    assert task.requested_action == "submit"
+    assert task.status == "ready_to_delegate"  # 无 missing_fields
+
+
+def test_resume_task_from_flow_marks_needs_confirmation_when_missing_fields():
+    flow = {
+        "fields": {"location": "武汉"},
+        "missing_fields": ["time_range", "reason"],
+    }
+    task = resume_task_from_flow("travel_application", flow)
+    assert task.missing_fields == ["time_range", "reason"]
+    assert task.status == "needs_confirmation"
+
+
+def test_attach_resumed_task_adds_task_and_thinking_event():
+    plan = StewardPlanResponse(
+        plan_id="plan_test",
+        planning_source="rule_fallback",
+        summary="占位",
+        tasks=[],
+        thinking_events=[],
+        pending_flow_confirmation={"status": "none"},
+    )
+    state = _state_with_travel_application({"location": "上海", "time_range": "2026-02-20 至 2026-02-23"})
+    updated = attach_resumed_task(plan, state, "travel_application")
+    assert len(updated.tasks) == 1
+    assert updated.tasks[0].task_type == "expense_application"
+    assert updated.tasks[0].ontology_fields["location"] == "上海"
+    assert updated.planning_source == "context_resume"
+    # thinking_event 应说明上下文已恢复
+    assert any("恢复" in event.title or "恢复" in event.content for event in updated.thinking_events)
+
+
+def test_attach_resumed_task_returns_unchanged_when_flow_missing():
+    plan = StewardPlanResponse(
+        plan_id="plan_test",
+        planning_source="rule_fallback",
+        summary="占位",
+        tasks=[],
+        thinking_events=[],
+        pending_flow_confirmation={"status": "none"},
+    )
+    updated = attach_resumed_task(plan, {"flows": {}}, "travel_application")
+    assert updated is plan  # 原样返回
+
+
+def test_resume_keywords_cover_common_variants():
+    # 确认关键词覆盖场景里常见的表述
+    assert "再提交" in RESUME_CONFIRMATION_KEYWORDS
+    assert "继续提交" in RESUME_CONFIRMATION_KEYWORDS
+    assert "重新申请" in RESUME_CONFIRMATION_KEYWORDS
+    # "提交" 单独不在列表里（避免把"首次提交"误判为恢复）
+    assert "提交" not in RESUME_CONFIRMATION_KEYWORDS

server/tests/test_steward_intent_agent.py

@@ -98,3 +98,58 @@ def test_steward_intent_system_prompt_mentions_query_intent_guidance() -> None:
     assert "query_travel_standard" in system_prompt
     assert "差旅" in system_prompt
     assert "住宿标准" in system_prompt
+
+
+def test_steward_intent_system_prompt_includes_conversation_history_guidance() -> None:
+    """system prompt 应包含'结合对话历史理解确认类话术'的引导。"""
+    from app.services import steward_intent_bootstrap  # noqa: F401
+
+    messages = StewardIntentAgent._build_messages(
+        StewardPlanRequest(message="再提交"),
+        base_date=__import__("datetime").date(2026, 6, 24),
+        canonical_fields=["location", "time_range"],
+    )
+    system_prompt = messages[0]["content"]
+    assert "recent_history" in system_prompt
+    assert "再提交" in system_prompt
+    assert "确认类话术" in system_prompt
+
+
+def test_steward_intent_context_payload_includes_recent_history() -> None:
+    """context_payload 应携带 recent_history 结构化字段（role + content）。"""
+    import json
+
+    request = StewardPlanRequest(
+        message="再提交",
+        context_json={
+            "recent_history": [
+                {"role": "user", "content": "2026-02-20 至 2026-02-23，去上海出差，火车"},
+                {"role": "assistant", "content": "好的，为您整理出差申请预览。"},
+                {"role": "user", "content": "直接提交"},
+                {"role": "assistant", "content": "检测到重复申请，已暂停提交。"},
+            ],
+        },
+    )
+    messages = StewardIntentAgent._build_messages(
+        request,
+        base_date=__import__("datetime").date(2026, 6, 24),
+        canonical_fields=["location", "time_range"],
+    )
+    user_payload = json.loads(messages[1]["content"])
+    assert "recent_history" in user_payload
+    assert len(user_payload["recent_history"]) == 4
+    assert user_payload["recent_history"][0]["role"] == "user"
+    assert "上海" in user_payload["recent_history"][0]["content"]
+
+
+def test_steward_intent_context_payload_omits_empty_recent_history() -> None:
+    """无 recent_history 时不应注入空列表。"""
+    import json
+
+    messages = StewardIntentAgent._build_messages(
+        StewardPlanRequest(message="你好"),
+        base_date=__import__("datetime").date(2026, 6, 24),
+        canonical_fields=["location"],
+    )
+    user_payload = json.loads(messages[1]["content"])
+    assert user_payload.get("recent_history", []) == []