ui(chat): scope the 1400px chat cap to message items via .container > *

Replaces the previous .chatSectionFlex column cap, which also squeezed the
input bar, approval panels, and other siblings. Now only direct children of
the message scroller are width-limited (centered, responsive below); the
input bar keeps its own 1000px rule and the scrollbar stays at the viewport
edge. Works for both the plain and Virtuoso scrollers (shared .container).

Author: weiesky.wangc

src/components/chat/ChatView.module.css

@@ -14,6 +14,16 @@
   flex-direction: column;
   -webkit-overflow-scrolling: touch;
   overscroll-behavior: contain;
+  /* 宽屏下消息列限宽 1400px 并居中；> 选择器只收窄直接子元素（消息项），
+     不影响 sticky 按钮 / roleFilterBar / 审批面板 / 输入条等兄弟区域。
+     双滚动容器（普通 .container 与 Virtuoso Scroller）共用本类，一处生效。 */
+  & > * {
+    max-width: 1400px;
+    margin-left: auto;
+    margin-right: auto;
+    width: 100%;
+    box-sizing: border-box;
+  }
 }
 
 .mobileVirtuoso {
@@ -363,10 +373,6 @@
   flex-direction: column;
   overflow: hidden;
   position: relative;
-  /* 宽屏下对话内容列限宽 1400px 并居中，窄屏自适应收缩 */
-  max-width: 1400px;
-  margin: 0 auto;
-  width: 100%;
 }
 
 /* 审批面板 + ChatInputBar 的共享定位容器。面板用 absolute bottom:100% 贴在输入栏之上。