fix(repl): queue prompt guidance for next turn (#333)

Keep normal prompt submissions during generation queued instead of interrupting the current turn. Add a visible next-turn banner in the prompt area so users can tell their follow-up guidance was accepted, and cover the new behavior with focused tests.

Fixes #328

Co-authored-by: Claude <noreply@anthropic.com>

src/components/PromptInput/PromptInputQueuedCommands.test.tsx

@@ -0,0 +1,35 @@
+import React from 'react'
+import { afterEach, beforeEach, describe, expect, it, mock } from 'bun:test'
+import { renderToString } from '../../utils/staticRender.js'
+
+describe('PromptInputQueuedCommands', () => {
+  beforeEach(() => {
+    mock.module('../../hooks/useCommandQueue.js', () => ({
+      useCommandQueue: () => [
+        {
+          value: 'Use another library',
+          mode: 'prompt',
+        },
+      ],
+    }))
+
+    mock.module('src/state/AppState.js', () => ({
+      useAppState: (
+        selector: (state: { viewingAgentTaskId?: string; isBriefOnly: boolean }) => unknown,
+      ) => selector({ viewingAgentTaskId: undefined, isBriefOnly: false }),
+    }))
+  })
+
+  afterEach(() => {
+    mock.restore()
+  })
+
+  it('shows a next-turn guidance banner for queued prompt messages', async () => {
+    const { PromptInputQueuedCommands } = await import('./PromptInputQueuedCommands.js')
+
+    const output = await renderToString(<PromptInputQueuedCommands />, 100)
+
+    expect(output).toContain('1 message queued for next turn')
+    expect(output).toContain('Use another library')
+  })
+})