Prevent page overscroll in chat layout (#1034)

Co-authored-by: vhqtvn <8930337+vhqtvn@users.noreply.github.com>

packages/ui/src/styles/design-system.css

@@ -125,11 +125,11 @@
     font-weight: var(--ui-regular-font-weight, 400);
   }
 
-  /* Desktop shell: prevent rubber-band scrolling of the page itself.
+  /* Prevent rubber-band scrolling of the page itself.
      App scroll should live inside dedicated scroll containers. */
-  :root.desktop-runtime,
-  :root.desktop-runtime body,
-  :root.desktop-runtime #root {
+  :root,
+  :root body,
+  :root #root {
     height: 100%;
     overflow: hidden;
     overscroll-behavior: none;

packages/ui/src/styles/mobile.css

@@ -150,6 +150,11 @@
     -webkit-overflow-scrolling: touch;
   }
 
+  :root.mobile-pointer:not(.desktop-runtime) [data-page-scroll-lock="true"] {
+    overflow: hidden !important;
+    overscroll-behavior: none;
+  }
+
   /* Keep markdown code blocks horizontally scrollable on mobile. */
   :root.mobile-pointer:not(.desktop-runtime) .markdown-content [data-markdown="code-block-body"] {
     overflow-x: auto !important;