fix(agent): keep agent chat sidebar scroll container shrinkable (#18252)

web/src/pages/agent/chat/box.tsx

@@ -97,7 +97,10 @@ function AgentChatBox() {
   return (
     <>
       <section className="flex flex-1 flex-col px-5 min-h-0 pb-4">
-        <div className="flex-1 overflow-auto" ref={messageContainerRef}>
+        <div
+          className="flex-1 overflow-auto min-h-0"
+          ref={messageContainerRef}
+        >
           <div>
             {!sendLoading && <div data-testid="agent-run-idle" />}
             {/* <Spin spinning={sendLoading}> */}