fix: prevent send queue flicker when the agent is idle

Claim idle conversation inputs before publishing queue changes so immediately dispatched messages do not briefly appear as pending. Preserve busy conversation queueing and add a regression assertion for notification ordering.

Validation: 369 focused tests, typecheck, and changed-file lint passed. Full-suite runs timed out with failures in other modules; repository lint reports errors in the existing story-graph demo.

Release note: Fix a brief pending-queue flash when sending a message while the agent is idle.

src/main/ipc.ts

@@ -6947,13 +6947,12 @@ export function registerIpcHandlers(
         contextManager.remove(attachment.id)
       }
       rendererReadyConversationQueues.add(item.conversationId)
-      publishConversationQueueChange(item.conversationId)
       if (!isConversationExecuting(item.conversationId)) {
         readyConversationQueues.add(item.conversationId)
-        setTimeout(() => {
-          void pumpConversationQueue(item.conversationId)
-        }, 0)
+        // Claim idle sends before exposing pending items to the renderer.
+        void pumpConversationQueue(item.conversationId)
       }
+      publishConversationQueueChange(item.conversationId)
       return item
     }
   )