Vietnamese Telex IME input broken in TUI mode

### Environment
- OS: macOS
- kiro-cli: 2.0.1
- Input method: Vietnamese Telex (macOS built-in)

### Steps to Reproduce
1. Start `kiro-cli chat` (default TUI mode)
2. Switch to Vietnamese Telex input method
3. Type any Vietnamese word (e.g. "xin chào")

### Expected Behavior
TUI mode should correctly handle IME (Input Method Editor) compose sequences, allowing users to type Vietnamese (Telex/VNI) and other multi-keystroke input methods without dropping characters.
The behavior should match classic mode, where Vietnamese Telex input works correctly.

For example, typing "xin chaof" with Telex should produce "xin chào".

### Actual Behavior
Characters are dropped during the compose sequence. For example, typing "chaof" (Telex for "chào") results in missing characters like "cho" or "chao" — the diacritical composition fails and
intermediate keystrokes are lost.

This issue only occurs in TUI mode. Classic mode (`--classic` / `--legacy-mode`) handles Vietnamese Telex input correctly.

### Workaround
Use `kiro-cli chat --legacy-mode` or `kiro-cli --classic`.

### Root Cause (Suspected)
The new TUI (React/Ink-based) input handling does not support IME compose sequences correctly. Classic mode uses Rust-based readline which handles IME properly.

Reproduziere das Problem mit `kiro-cli chat` unter macOS und vietnamesischer Telex-Eingabe. Vergleiche anschließend den TUI-Eingabepfad mit dem klassischen Modus (`--legacy-mode` oder `--classic`), der Rust-basiertes readline verwendet. Untersuche die React/Ink-basierte TUI-Eingabeverarbeitung. Als abgeschlossen gilt die Arbeit, wenn Kompositionssequenzen keine Zeichen mehr verlieren und die vietnamesische Eingabe dem klassischen Modus entspricht.

Vom Indexierungsmodell aus dem Issue-Text verfasst.