feat(web): incremental render-window batch rendering engine

Add render_window.js: Python-driven incremental pagination with id+chainIndex state, anchor restore, batch guard and streaming auto-detect; wired through chat_bridge and the page shell.

ui/views/chat_bridge.py

@@ -9,6 +9,9 @@ class ChatBridge(QObject):
     delete_message_requested = pyqtSignal(str)     # 删除消息信号 (msg_id)
     attachment_clicked = pyqtSignal(str)
     scroll_changed = pyqtSignal(float, float, float)  # 页面 scrollY / scrollHeight / innerHeight
+    # 🆕 P1-01 渲染窗口：前端请求换页（fire-and-forget；响应经 run_js 推送）
+    window_page_requested = pyqtSignal(str, str, str, int)  # (session_id, direction, boundary_id, generation)
+
     def __init__(self, page, channel, js_runner=None):
         """
         :param page: QWebEnginePage 实例（QtWebEngine 路径）
@@ -18,6 +21,7 @@ class ChatBridge(QObject):
         super().__init__()
         self.page = page
         self._js_runner = js_runner
+        self.window = None  # 🆕 P1-01：MainWindow 引用（分页请求需要访问 DB/代次）
         if channel is not None:
             # 将自身注册到 channel 中，前端可通过 bridge 对象调用
             channel.registerObject("bridge", self)
@@ -157,8 +161,46 @@ class ChatBridge(QObject):
         """隐藏加载界面（带渐变退场）"""
         self.run_js("hideLoadingOverlay();")
 
+    # ---------- 🆕 P1-01 渲染窗口 (Python -> JS) ----------
+
+    def rw_config(self, mode: str, size: int):
+        """注入渲染窗口配置（JS 就绪后、首次加载前调用一次）"""
+        self.run_js("rwApplyConfig(" + json.dumps(
+            {"render_window_mode": mode, "render_window_size": size}) + ");")
+
+    def rw_begin(self, session_id: str, generation: int, total: int):
+        """开始一轮窗口化加载：清屏 + 重同步 (session, generation)"""
+        self.run_js(f"rwBegin({json.dumps(session_id)}, {int(generation)}, {int(total)});")
+
+    def rw_init_window(self, session_id: str, generation: int, chain_len: int, items):
+        """初始窗口就绪：items = [(msg_id, chain_index), ...]（旧→新）"""
+        payload = json.dumps({
+            "sessionId": session_id,
+            "generation": int(generation),
+            "chainLen": int(chain_len),
+            "items": [{"id": mid, "chainIndex": ix} for mid, ix in items],
+        }, ensure_ascii=False)
+        self.run_js(f"rwInitWindow({payload});")
+
+    def rw_note_live(self, session_id: str, generation: int, msg_id: str,
+                     chain_index: int, chain_len: int = -1):
+        """新消息追加进窗口（发送用户消息 / 助手占位 / 切回续流）。
+        未持久化/未知 → chain_index=-1；未知链长 → chain_len=-1（JS 保持旧值）"""
+        self.run_js(f"rwNoteLive({json.dumps(session_id)}, {int(generation)}, "
+                    f"{json.dumps(msg_id)}, {int(chain_index)}, {int(chain_len)});")
+
+    def rw_page_response(self, payload: dict):
+        """分页响应推送：payload 由 MainWindow._on_window_page_request 构造"""
+        self.run_js("rwPageResponse(" + json.dumps(payload, ensure_ascii=False) + ");")
+
     # ---------- 交互 Slot (JS -> Python) ----------
 
+    @pyqtSlot(str, str, str, int)
+    def onRequestWindowPage(self, session_id, direction, boundary_msg_id, generation):
+        """🆕 P1-01：前端请求换页（direction: older/newer）。
+        fire-and-forget：结果由 Python 经 rwPageResponse 推送（双引擎同构）。"""
+        self.window_page_requested.emit(session_id, direction, boundary_msg_id, int(generation))
+
     @pyqtSlot(str)
     def onRegenerateClicked(self, msg_id):
         """前端点击“重新生成”按钮时触发"""