feat(agent-office): 우측 기본 패널을 횡단 타임라인으로 교체

src/pages/agent-office/AgentOffice.jsx

@@ -6,6 +6,7 @@ import TopBar from './components/TopBar.jsx';
 import AgentGrid from './components/AgentGrid.jsx';
 import SidePanel from './components/SidePanel.jsx';
 import EmptyDetailPanel from './components/EmptyDetailPanel.jsx';
+import ActivityTimeline from './components/ActivityTimeline.jsx';
 import './AgentOffice.css';
 
 export default function AgentOffice() {
@@ -36,7 +37,12 @@ export default function AgentOffice() {
 
   let rightPanel;
   if (selectedAgent === null) {
-    rightPanel = <EmptyDetailPanel variant="initial" />;
+    rightPanel = (
+      <ActivityTimeline
+        refreshTrigger={refreshTrigger}
+        onSelectAgent={handleSelectAgent}
+      />
+    );
   } else if (selectedAgent.startsWith('placeholder-')) {
     rightPanel = <EmptyDetailPanel variant="placeholder" onClose={handleClose} />;
   } else {