fix(quick-pane): hide empty exchange frame

ui/src/quick-pane/QuickPane.tsx

@@ -260,6 +260,17 @@ export default function QuickPane() {
     activityPhase === "Thinking"
       ? `${activityPhase} · ${elapsedSeconds}s`
       : activityPhase;
+  const hasExchangeContent =
+    messages.length > 0 ||
+    runActive ||
+    responseComplete ||
+    !!activity ||
+    !!escalation ||
+    !!error ||
+    !!catalogError ||
+    !!notice ||
+    !!catalogNotice ||
+    !!extension;
 
   useEffect(() => {
     setThinkingLevel((current) =>
@@ -1004,7 +1015,7 @@ export default function QuickPane() {
       </div>
 
       <section
-        className="quick-pane-exchange"
+        className={`quick-pane-exchange${hasExchangeContent ? "" : " empty"}`}
         aria-label="Quick exchange"
         ref={exchangeRef}
       >

ui/src/quick-pane/quick-pane.css

@@ -210,6 +210,10 @@ body {
   scroll-behavior: smooth;
 }
 
+.quick-pane-exchange.empty {
+  display: none;
+}
+
 .quick-pane-transcript {
   display: flex;
   min-height: 0;