修复「新对话」流式中无法重置 + 参考文献开关默认关闭并加对勾

- 流式回答过程中点「新对话」:URL 同路径导致 react-router navigate 静默 no-op,
  下游 hook 收不到事件;改为显式 navigate(..., {replace:true, state:{resetAt}})
  保证每次点击刷新 location.key,并让 useThreadChat 监听 location.key 触发重置
- useThreadStream 在 threadId 变化时 stop() 掉上一条 SSE,避免旧流继续派发事件
- 引入 KeyedChatPage 用 location.key 作 ChatRuntime key,真正的导航触发整树 remount,
  解决 useStream 内部 stream.values 残留导致欢迎页底下还能看到旧消息的过渡帧问题
- 「参考文献」开关默认关闭(local.ts),开启态在文字前额外多一个 ✓ 对勾

frontend-web/src/core/settings/local.ts

@@ -4,10 +4,10 @@ export const DEFAULT_LOCAL_SETTINGS: LocalSettings = {
   notification: {
     enabled: true,
   },
-  display: {
-    streamSpeedMeterEnabled: true,
-    ragModeEnabled: true,
-  },
+  display: {
+    streamSpeedMeterEnabled: true,
+    ragModeEnabled: false,
+  },
   context: {
     model_name: undefined,
     mode: undefined,
@@ -33,13 +33,13 @@ export interface LocalSettings {
      * AI reply is in flight. Default on; controlled by the user from
      * the appearance settings page.
      */
-    streamSpeedMeterEnabled: boolean;
-    /**
-     * Global switch for skill result display adapters. When disabled, chat
-     * messages render tool results with the legacy generic search UI only.
-     */
-    ragModeEnabled: boolean;
-  };
+    streamSpeedMeterEnabled: boolean;
+    /**
+     * Global switch for skill result display adapters. When disabled, chat
+     * messages render tool results with the legacy generic search UI only.
+     */
+    ragModeEnabled: boolean;
+  };
   context: Omit<
     AgentThreadContext,
     | "thread_id"