feat: Streamlit多轮对话界面 + 集成测试

app.py:
  侧边栏：会话管理（创建/切换/删除）、快捷操作（预览/撤销/重置）、
         配置信息、JRXML下载
  主区域：多轮聊天、8种意图差异化展示（JRXML代码/咨询回答/
          错误解释/成功提示）
  URL参数：?session_id= 会话分享

tests/:
  test_validation.py: 验证服务6个单元测试（健康检查/空内容/
                      无效XML/缺少尺寸/有效JRXML/字段引用）
  test_agent.py: 5个集成验收场景（简单生成/自动修正/
                  多轮修改/上下文感知修改/最大重试处理）

app.py

@@ -0,0 +1,318 @@
+"""Streamlit 多轮对话 UI，用于 JRXML 生成代理。"""
+
+import os
+import sys
+
+import streamlit as st
+
+from dotenv import load_dotenv
+load_dotenv()
+
+from agent.graph import build_graph, create_initial_state
+from backend.session import (
+    create_session,
+    load_session,
+    delete_session,
+    list_all_sessions,
+)
+
+st.set_page_config(
+    page_title="JRXML 代理",
+    page_icon="📊",
+    layout="wide",
+    initial_sidebar_state="expanded",
+)
+
+# ---- URL 参数：session_id ----
+query_params = st.query_params
+url_session_id = query_params.get("session_id", "")
+
+# ---- 会话状态初始化 ----
+if "messages" not in st.session_state:
+    st.session_state.messages = []
+if "graph" not in st.session_state:
+    st.session_state.graph = build_graph()
+if "pending_action" not in st.session_state:
+    st.session_state.pending_action = None
+
+# 确定活跃的 session_id
+if "agent_state" not in st.session_state:
+    if url_session_id:
+        data = load_session(url_session_id)
+        if data and data.get("agent_state"):
+            st.session_state.agent_state = data["agent_state"]
+            st.session_state.agent_state["session_id"] = url_session_id
+        else:
+            st.session_state.agent_state = create_initial_state()
+            new_data = create_session(name="", agent_state=st.session_state.agent_state)
+            st.session_state.agent_state["session_id"] = new_data["session_id"]
+            st.session_state.agent_state["session_name"] = new_data["session_name"]
+            st.session_state.agent_state["created_at"] = new_data["created_at"]
+    else:
+        st.session_state.agent_state = create_initial_state()
+        new_data = create_session(name="", agent_state=st.session_state.agent_state)
+        st.session_state.agent_state["session_id"] = new_data["session_id"]
+        st.session_state.agent_state["session_name"] = new_data["session_name"]
+        st.session_state.agent_state["created_at"] = new_data["created_at"]
+
+current_session_id = st.session_state.agent_state.get("session_id", "")
+
+
+def run_agent(user_input: str) -> dict:
+    """运行代理图，返回最终状态。"""
+    agent_state = st.session_state.agent_state
+
+    if agent_state.get("current_jrxml") and agent_state.get("status") == "pass":
+        agent_state["user_modification_request"] = user_input
+
+    agent_state["user_input"] = user_input
+    agent_state["retry_count"] = 0
+
+    final_state = None
+    with st.chat_message("assistant"):
+        status_placeholder = st.empty()
+        jrxml_placeholder = st.empty()
+
+        for event in st.session_state.graph.stream(agent_state):
+            for node_name, node_state in event.items():
+                final_state = node_state
+                if node_name == "classify_intent":
+                    intent = node_state.get("intent", "")
+                    intent_labels = {
+                        "initial_generation": "🆕 识别为新建报表请求",
+                        "modify_report": "✏️ 识别为修改报表请求",
+                        "preview_report": "👁 识别为预览请求",
+                        "export_pdf": "📄 识别为导出PDF请求",
+                        "export_jrxml": "📥 识别为导出JRXML请求",
+                        "undo_modification": "↩ 识别为撤销请求",
+                        "consult_question": "💬 识别为咨询问题",
+                        "reset_session": "🔄 识别为重置会话请求",
+                    }
+                    label = intent_labels.get(intent, f"🔍 意图: {intent}")
+                    status_placeholder.info(label)
+                elif node_name == "generate":
+                    status_placeholder.info("🔧 正在生成 JRXML...")
+                elif node_name == "modify_jrxml":
+                    status_placeholder.info("🔧 正在根据您的请求修改 JRXML...")
+                elif node_name == "validate":
+                    if node_state.get("status") == "pass":
+                        status_placeholder.success("✅ 验证通过！")
+                    else:
+                        status_placeholder.warning("⚠ 验证失败，正在分析错误...")
+                elif node_name == "explain_error":
+                    explanation = node_state.get("natural_explanation", "")
+                    status_placeholder.warning(f"🔍 {explanation}")
+                elif node_name == "correct_jrxml":
+                    status_placeholder.info(f"🛠 正在自动修正（尝试 {node_state.get('retry_count', 1)}）...")
+                elif node_name == "handle_consult":
+                    pass
+                elif node_name == "handle_undo":
+                    status_placeholder.info("↩ 已撤销上一步修改")
+                elif node_name == "handle_reset":
+                    status_placeholder.info("🔄 会话已重置")
+                elif node_name == "manage_context":
+                    pass
+                elif node_name == "save_state_snapshot":
+                    pass
+                elif node_name == "save_session":
+                    pass
+                elif node_name == "finalize":
+                    pass
+
+        if final_state:
+            st.session_state.agent_state = final_state
+            intent = final_state.get("intent", "")
+
+            if intent == "consult_question":
+                answer = final_state.get("consult_answer", "")
+                st.session_state.messages.append({
+                    "role": "assistant",
+                    "content": answer,
+                    "type": "consult",
+                })
+                status_placeholder.empty()
+                st.markdown(answer)
+            elif intent in ("undo_modification", "reset_session"):
+                # 消息已在节点中添加，不需要额外输出
+                status_placeholder.empty()
+                jrxml_placeholder.empty()
+            elif intent in ("preview_report", "export_pdf", "export_jrxml"):
+                jrxml = final_state.get("current_jrxml", "")
+                if jrxml:
+                    st.session_state.messages.append({
+                        "role": "assistant",
+                        "content": jrxml,
+                        "type": "jrxml",
+                    })
+                    status_placeholder.success("✅ 当前报表")
+                    jrxml_placeholder.code(jrxml, language="xml")
+                else:
+                    status_placeholder.warning("⚠ 当前没有报表可以预览或导出。")
+                    jrxml_placeholder.empty()
+            elif final_state.get("status") == "pass":
+                st.session_state.messages.append({
+                    "role": "assistant",
+                    "content": final_state.get("current_jrxml", ""),
+                    "type": "jrxml",
+                })
+                st.session_state.messages.append({
+                    "role": "assistant",
+                    "content": "✅ JRXML 生成成功！您可以从侧边栏下载文件，或继续修改。",
+                    "type": "success",
+                })
+                status_placeholder.success("✅ JRXML 验证通过！")
+                jrxml_placeholder.code(final_state.get("current_jrxml", ""), language="xml")
+            else:
+                error_msg = final_state.get("error_msg", "未知错误")
+                explanation = final_state.get("natural_explanation", "")
+                retries = final_state.get("retry_count", 0)
+                st.session_state.messages.append({
+                    "role": "assistant",
+                    "content": final_state.get("current_jrxml", ""),
+                    "type": "jrxml",
+                })
+                st.session_state.messages.append({
+                    "role": "assistant",
+                    "content": f"❌ 经过 {retries} 次重试后仍无法生成有效的 JRXML。\n\n**错误:** {error_msg}\n\n**解释:** {explanation}\n\n请重新描述您的需求或简化报表结构。",
+                    "type": "error_explanation",
+                })
+                status_placeholder.error(f"❌ 经过 {retries} 次重试后验证失败")
+                jrxml_placeholder.text("")
+        else:
+            st.error("未产生结果，请重试。")
+
+    return final_state
+
+
+# ---- 侧边栏 ----
+with st.sidebar:
+    st.title("📊 JRXML 代理")
+    st.markdown("通过自然语言生成 JasperReports 模板。")
+    st.divider()
+
+    # 会话管理
+    st.markdown("### 会话管理")
+
+    sessions = list_all_sessions()
+    session_options = {}
+    for s in sessions:
+        sid = s["session_id"]
+        name = s.get("session_name", sid)
+        updated = s.get("updated_at", "")[:16]
+        session_options[f"{name} ({updated})"] = sid
+
+    selected_label = None
+    for label, sid in session_options.items():
+        if sid == current_session_id:
+            selected_label = label
+            break
+
+    selected = st.selectbox(
+        "切换会话",
+        options=list(session_options.keys()),
+        index=list(session_options.keys()).index(selected_label) if selected_label else 0,
+        key="session_selector",
+    )
+
+    if selected and session_options.get(selected) != current_session_id:
+        new_sid = session_options[selected]
+        data = load_session(new_sid)
+        if data and data.get("agent_state"):
+            st.session_state.agent_state = data["agent_state"]
+            st.session_state.messages = []
+            st.rerun()
+
+    col1, col2 = st.columns(2)
+    with col1:
+        if st.button("➕ 新建", use_container_width=True):
+            new_data = create_session(name="", agent_state=create_initial_state())
+            st.session_state.agent_state = create_initial_state()
+            st.session_state.agent_state["session_id"] = new_data["session_id"]
+            st.session_state.agent_state["session_name"] = new_data["session_name"]
+            st.session_state.agent_state["created_at"] = new_data["created_at"]
+            st.session_state.messages = []
+            st.rerun()
+    with col2:
+        if st.button("🗑 删除", use_container_width=True):
+            if current_session_id:
+                delete_session(current_session_id)
+            st.session_state.agent_state = create_initial_state()
+            new_data = create_session(name="", agent_state=st.session_state.agent_state)
+            st.session_state.agent_state["session_id"] = new_data["session_id"]
+            st.session_state.agent_state["session_name"] = new_data["session_name"]
+            st.session_state.agent_state["created_at"] = new_data["created_at"]
+            st.session_state.messages = []
+            st.rerun()
+
+    current_name = st.session_state.agent_state.get("session_name", "")
+    st.caption(f"当前: {current_name} (`{current_session_id}`)")
+
+    st.divider()
+    st.markdown("### 快捷操作")
+
+    has_jrxml = bool(st.session_state.agent_state.get("current_jrxml", "").strip())
+    has_history = bool(st.session_state.agent_state.get("history_states", []))
+
+    qcol1, qcol2 = st.columns(2)
+    with qcol1:
+        if st.button("👁 预览", use_container_width=True, disabled=not has_jrxml):
+            with st.spinner("正在准备预览..."):
+                run_agent("预览报表")
+            st.rerun()
+    with qcol2:
+        if st.button("↩ 撤销", use_container_width=True, disabled=not has_history):
+            with st.spinner("正在撤销..."):
+                run_agent("撤销上一步修改")
+            st.rerun()
+
+    if st.button("🔄 重置会话", use_container_width=True):
+        with st.spinner("正在重置..."):
+            run_agent("重新来，清空当前报表")
+        st.rerun()
+
+    st.divider()
+    st.markdown("### 配置")
+    llm_backend = os.getenv("LLM_BACKEND", "cloud")
+    llm_model = os.getenv("LLM_MODEL", os.getenv("LOCAL_LLM_MODEL", "gpt-4o"))
+    st.caption(f"大语言模型: {llm_backend} / {llm_model}")
+    st.caption(f"最大重试次数: {os.getenv('MAX_RETRY', '3')}")
+    st.caption(f"验证服务: {os.getenv('VALIDATION_SERVICE_URL', 'http://localhost:8001/validate')}")
+
+    st.divider()
+    st.markdown("### 下载")
+    final = st.session_state.agent_state.get("final_jrxml", "")
+    if final:
+        st.download_button(
+            label="📥 下载 JRXML",
+            data=final,
+            file_name="report.jrxml",
+            mime="application/xml",
+            use_container_width=True,
+        )
+
+# ---- 标题 ----
+st.title("📝 JRXML 报表生成器")
+st.caption("用自然语言描述您的报表需求，我将逐步生成可用的 JRXML 模板。")
+
+# ---- 聊天历史 ----
+for msg in st.session_state.messages:
+    with st.chat_message(msg["role"]):
+        if msg["role"] == "assistant" and msg.get("type") == "jrxml":
+            with st.expander("查看生成的 JRXML", expanded=False):
+                st.code(msg["content"], language="xml")
+        elif msg["role"] == "assistant" and msg.get("type") == "error_explanation":
+            st.warning(msg["content"])
+        elif msg["role"] == "assistant" and msg.get("type") == "success":
+            st.success(msg["content"])
+        elif msg["role"] == "assistant" and msg.get("type") == "consult":
+            st.info(msg["content"])
+        else:
+            st.markdown(msg["content"])
+
+# ---- 聊天输入 ----
+if prompt := st.chat_input("描述您的报表需求..."):
+    st.session_state.messages.append({"role": "user", "content": prompt})
+    with st.chat_message("user"):
+        st.markdown(prompt)
+    run_agent(prompt)
+    st.rerun()