fix: OCR字段提取集成修复 + 会话切换无限循环修复 + 一键启动脚本

- process_input 传入17个默认中文字段（修复空列表导致零字段提取）
- OCR提取结果自动注入 LLM 上下文
- save_session_node/load_session_node 持久化 session_id（修复切换会话无限 rerun）
- app.py 会话切换后显式设置 session_id（纵深防御）
- 新增 start.bat / stop.bat 一键启动/停止脚本
- 更新 CLAUDE.md + CODE_GUIDE.md 文档

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

agent/nodes.py

@@ -123,7 +123,13 @@ def process_input(state: AgentState) -> Dict:
             try:
                 from backend.ocr_extractor import OcrExtractor
                 extractor = OcrExtractor()
-                ocr_result = extractor.extract(uploaded_path, [])
+                default_fields = [
+                    "发票代码", "发票号码", "开票日期", "合计金额", "校验码",
+                    "价税合计", "总金额", "日期", "金额", "数量", "单价", "税率",
+                    "购买方名称", "销售方名称", "货物名称", "规格型号",
+                    "不含税金额", "税额",
+                ]
+                ocr_result = extractor.extract(uploaded_path, default_fields)
                 if ocr_result.get("ocr_available"):
                     state["ocr_extraction_result"] = ocr_result
                     _node_log.info(
@@ -134,6 +140,20 @@ def process_input(state: AgentState) -> Dict:
                             "fields": len(ocr_result.get("fields", [])),
                         },
                     )
+                    # 将提取到的字段注入到对话上下文，供 LLM 使用
+                    extracted_fields = ocr_result.get("fields", [])
+                    non_empty = [f for f in extracted_fields if f.get("field_value")]
+                    if non_empty:
+                        lines = ["[OCR 单据字段提取结果]"]
+                        for f in non_empty:
+                            lines.append(
+                                f"- {f['field_name']}: {f['field_value']}"
+                                f"（置信度: {f['confidence']:.0%}, 方法: {f['extraction_method']}）"
+                            )
+                        ocr_context = "\n".join(lines)
+                        user_input = f"{ocr_context}\n\n{user_input}"
+                        # 同时更新工作对话历史中的最后一条
+                        conv_history[-1]["content"] = user_input
             except Exception as e:
                 _node_log.warning(f"OCR 字段提取失败: {e}")
                 state["ocr_extraction_result"] = {"error": str(e)}
@@ -357,7 +377,7 @@ def load_session_node(state: AgentState) -> Dict:
         if data and data.get("agent_state"):
             saved = data["agent_state"]
             # 恢复核心字段（不覆盖当前请求的 user_input / stage）
-            for key in ("conversation_history", "full_conversation_history",
+            for key in ("session_id", "conversation_history", "full_conversation_history",
                         "current_jrxml", "final_jrxml", "compressed_history",
                         "session_name", "created_at", "history_states"):
                 if key in saved and key not in ("user_input", "stage"):
@@ -379,7 +399,7 @@ def save_session_node(state: AgentState) -> Dict:
     try:
         from backend.session import save_session
         persistable = {}
-        for key in ("conversation_history", "full_conversation_history",
+        for key in ("session_id", "conversation_history", "full_conversation_history",
                     "current_jrxml", "final_jrxml", "compressed_history",
                     "status", "error_msg", "history_states"):
             if key in state: