fix: improve agent activity reporting

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/renderer/lib/sessionActivity.ts

@@ -42,15 +42,11 @@ export function applySessionEventActivity(
   }
 
   if (event.kind === 'status') {
-    if (event.status === 'running' || event.status === 'idle' || event.status === 'error') {
+    if (event.status === 'running') {
       return removeSessionActivity(current, event.sessionId);
     }
   }
 
-  if (event.kind === 'error') {
-    return removeSessionActivity(current, event.sessionId);
-  }
-
   return current;
 }