fix: resolve CJK composition bug on iOS terminals (backspace packet splitting)

[liante0904]

Why this is needed

iOS terminal apps such as Moshi and Blink send CJK (Chinese, Japanese, Korean) composed characters in a single TCP packet when the iOS keyboard composes syllables. For example, when a user types the Korean syllable "가" followed by "나", the terminal may transmit the byte sequence:

"가\x7f나"   (character U+AC00 + backspace 0x7f + character U+B098)

The current handleData in useTerminalInput.ts passes the entire concatenated buffer to parseTerminalInput() without splitting. Since parseTerminalInput treats the whole string as a single input event, the intermediate backspace (\x7f) is not interpreted as a delete action, and the composed character sequence gets corrupted. This results in garbled text and broken CJK input on iOS terminals.

This is a long-standing, well-known issue affecting CJK users of Node.js TUI applications.

What was changed

In src/ui/prompt/useTerminalInput.ts, the handleData function now detects packets that contain one or more \x7f (backspace) bytes alongside other characters. When such a combined packet is received:

1. The packet is split on \x7f.
2. Each segment is dispatched individually through parseTerminalInput() and the input handler, in order:
   • First the initial character(s)
   • Then a properly parsed backspace event
   • Then the subsequent character(s)
   • (Repeating for multiple composition steps in a single packet)

Normal input (without embedded backspaces) follows the original code path with zero overhead.

Before

const handleData = (data: Buffer | string) => {
  const { input, key } = parseTerminalInput(data);
  handlerRef.current(input, key);
};

After

const handleData = (data: Buffer | string) => {
  const raw = String(data);

  if (raw.includes("\x7f") && raw.length > 1) {
    const parts = raw.split("\x7f");
    if (parts[0]) {
      const { input, key } = parseTerminalInput(parts[0]);
      handlerRef.current(input, key);
    }
    for (let i = 1; i < parts.length; i++) {
      const bs = parseTerminalInput("\x7f");
      handlerRef.current(bs.input, bs.key);
      if (parts[i]) {
        const { input, key } = parseTerminalInput(parts[i]);
        handlerRef.current(input, key);
      }
    }
    return;
  }

  const { input, key } = parseTerminalInput(data);
  handlerRef.current(input, key);
};

Testing

• npm run typecheck passes with no errors.
• eslint --fix and prettier --write pass via pre-commit hooks.