feat(tui): add multiline paste mode in minimal UI

src/frontends/tui/minimal.test.ts

@@ -37,6 +37,7 @@ function minimalTuiPrivates(value: MinimalTui): {
   handleVerboseCommand: () => void;
   handleToolEvent: (event: unknown) => void;
   handleCommand: (command: unknown) => Promise<void>;
+  handleMessage: (content: string) => Promise<void>;
   handleEscapeAction: () => boolean;
   handleCtrlCPress: (nowMs?: number) => boolean;
   clearSubmittedPromptLine: () => boolean;
@@ -60,6 +61,7 @@ function minimalTuiPrivates(value: MinimalTui): {
     handleVerboseCommand: () => void;
     handleToolEvent: (event: unknown) => void;
     handleCommand: (command: unknown) => Promise<void>;
+    handleMessage: (content: string) => Promise<void>;
     handleEscapeAction: () => boolean;
     handleCtrlCPress: (nowMs?: number) => boolean;
     clearSubmittedPromptLine: () => boolean;
@@ -401,6 +403,48 @@ describe('MinimalTui backend command', () => {
     }
   });
 
+  it('collects multiline input from /paste and sends as one message', async () => {
+    const mockSession = {
+      id: 'test',
+      getHistory: () => [],
+      addMessage: vi.fn(),
+      clear: vi.fn(),
+      replaceHistory: vi.fn(),
+    };
+    const logSpy = vi.spyOn(console, 'log').mockImplementation(() => {});
+    try {
+      const tui = new MinimalTui({
+        session: asSession(mockSession),
+        modelClient: asModelClient({}),
+        systemPrompt: 'test',
+      });
+
+      const promptSpy = vi.fn()
+        .mockResolvedValueOnce('first line')
+        .mockResolvedValueOnce('second line')
+        .mockResolvedValueOnce('.');
+      minimalTuiPrivates(tui).prompt = promptSpy;
+
+      const handleMessageSpy = vi.fn(async () => {});
+      minimalTuiPrivates(tui).handleMessage = handleMessageSpy;
+      minimalTuiPrivates(tui).running = true;
+      minimalTuiPrivates(tui).rl = {
+        once: vi.fn(),
+        removeListener: vi.fn(),
+        question: vi.fn(),
+        write: vi.fn(),
+        prompt: vi.fn(),
+      };
+
+      await minimalTuiPrivates(tui).handleCommand({ type: 'multiline' });
+
+      expect(handleMessageSpy).toHaveBeenCalledWith('first line\nsecond line');
+      expect(promptSpy).toHaveBeenCalledTimes(3);
+    } finally {
+      logSpy.mockRestore();
+    }
+  });
+
   it('only renders tool activity when verbose mode is enabled', () => {
     const mockSession = {
       id: 'test',