feat(tui): add Esc key to cancel active prompt without exiting

src/frontends/tui/minimal.test.ts

@@ -29,10 +29,26 @@ function asAgent(value: unknown): NativeAgent {
 function minimalTuiPrivates(value: MinimalTui): {
   handleBackendCommand: (provider: string) => Promise<void>;
   handleModelCommand: (tier: string, providerModel?: string) => void;
+  prompt: (text: string) => Promise<string>;
+  rl: {
+    once: (event: string, cb: () => void) => void;
+    removeListener: (event: string, cb: () => void) => void;
+    question: (text: string, cb: (answer: string) => void) => void;
+    write: (data: string | null, key?: { ctrl?: boolean; name?: string }) => void;
+  };
+  activePromptCancel: (() => void) | null;
 } {
   return value as unknown as {
     handleBackendCommand: (provider: string) => Promise<void>;
     handleModelCommand: (tier: string, providerModel?: string) => void;
+    prompt: (text: string) => Promise<string>;
+    rl: {
+      once: (event: string, cb: () => void) => void;
+      removeListener: (event: string, cb: () => void) => void;
+      question: (text: string, cb: (answer: string) => void) => void;
+      write: (data: string | null, key?: { ctrl?: boolean; name?: string }) => void;
+    };
+    activePromptCancel: (() => void) | null;
   };
 }
 
@@ -270,3 +286,47 @@ describe('MinimalTui backend command', () => {
     }
   });
 });
+
+describe('MinimalTui prompt cancellation', () => {
+  it('cancels an active prompt without closing the TUI', async () => {
+    const mockSession = {
+      id: 'test',
+      getHistory: () => [],
+      addMessage: vi.fn(),
+      clear: vi.fn(),
+      replaceHistory: vi.fn(),
+    };
+
+    const tui = new MinimalTui({
+      session: asSession(mockSession),
+      modelClient: asRouter({}),
+      systemPrompt: 'test',
+    });
+
+    let onAnswer: ((answer: string) => void) | undefined;
+    const write = vi.fn((_: string | null, key?: { ctrl?: boolean; name?: string }) => {
+      if (key?.name === 'return') {
+        onAnswer?.('');
+      }
+    });
+
+    minimalTuiPrivates(tui).rl = {
+      once: vi.fn(),
+      removeListener: vi.fn(),
+      question: vi.fn((_text: string, cb: (answer: string) => void) => {
+        onAnswer = cb;
+      }),
+      write,
+    };
+
+    const promptPromise = minimalTuiPrivates(tui).prompt('Confirm? ');
+    expect(minimalTuiPrivates(tui).activePromptCancel).toBeTypeOf('function');
+
+    minimalTuiPrivates(tui).activePromptCancel?.();
+
+    await expect(promptPromise).resolves.toBe('');
+    expect(write).toHaveBeenCalledWith(null, { ctrl: true, name: 'u' });
+    expect(write).toHaveBeenCalledWith(null, { name: 'return' });
+    expect(minimalTuiPrivates(tui).activePromptCancel).toBeNull();
+  });
+});