fix(keypress): handle unsupported Kitty CSI-u keys and recover plain text

- Add helper functions for better code organization (createPrintableKey,
  getCompleteCsiSequenceLength, parsePlainTextPrefix)
- Drop unsupported Kitty CSI-u keys without blocking subsequent input
- Recover plain text that arrives in same chunk after unsupported CSI-u keys
- Add comprehensive tests for edge cases (CAPS_LOCK, event metadata variants)

Improves robustness of Kitty keyboard protocol parsing by gracefully
handling unsupported key codes and ensuring plain text input is not lost.

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

packages/cli/src/ui/contexts/KeypressContext.test.tsx

@@ -1367,6 +1367,75 @@ describe('KeypressContext - Kitty Protocol', () => {
         }),
       );
     });
+
+    it('drops unsupported Kitty CSI-u keys without blocking later input', () => {
+      const keyHandler = vi.fn();
+      const { result } = renderHook(() => useKeypressContext(), { wrapper });
+      act(() => result.current.subscribe(keyHandler));
+
+      act(() => stdin.sendKittySequence(`\x1b[57358u`)); // CAPS_LOCK
+      act(() =>
+        stdin.pressKey({
+          name: 'a',
+          ctrl: false,
+          meta: false,
+          shift: false,
+          paste: false,
+          sequence: 'a',
+        }),
+      );
+
+      expect(keyHandler).toHaveBeenCalledTimes(1);
+      expect(keyHandler).toHaveBeenCalledWith(
+        expect.objectContaining({
+          name: 'a',
+          sequence: 'a',
+        }),
+      );
+    });
+
+    it('recovers plain text that arrives in the same chunk after an unsupported CSI-u key', () => {
+      const keyHandler = vi.fn();
+      const { result } = renderHook(() => useKeypressContext(), { wrapper });
+      act(() => result.current.subscribe(keyHandler));
+
+      act(() =>
+        stdin.pressKey({
+          name: '',
+          ctrl: false,
+          meta: false,
+          shift: false,
+          paste: false,
+          sequence: '\x1b[57358ua',
+        }),
+      );
+
+      expect(keyHandler).toHaveBeenCalledTimes(1);
+      expect(keyHandler).toHaveBeenCalledWith(
+        expect.objectContaining({
+          name: 'a',
+          sequence: 'a',
+          kittyProtocol: true,
+        }),
+      );
+    });
+
+    it('drops unsupported CSI-u variants with event metadata and keeps parsing', () => {
+      const keyHandler = vi.fn();
+      const { result } = renderHook(() => useKeypressContext(), { wrapper });
+      act(() => result.current.subscribe(keyHandler));
+
+      act(() => stdin.sendKittySequence(`\x1b[57358;1:1u\x1b[100u`));
+
+      expect(keyHandler).toHaveBeenCalledTimes(1);
+      expect(keyHandler).toHaveBeenCalledWith(
+        expect.objectContaining({
+          name: 'd',
+          sequence: 'd',
+          kittyProtocol: true,
+        }),
+      );
+    });
   });
 
   describe('Kitty keypad private-use keys', () => {