Panic when truncating Korean (UTF-8 multibyte) strings

Bug Description

Claude Code CLI panics when handling strings containing Korean characters. The error occurs because the code attempts to slice a UTF-8 string at a byte index that falls in the middle of a multibyte character.

Error Message

thread '<unnamed>' panicked at /rustc/ed61e7d7e242494fb7057f2657300d9e77bb4fcb\library\core\src\str\mod.rs:833:21:
byte index 8 is not a char boundary; it is inside '트' (bytes 6..9) of `이언트 (OC=kazzang)`
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Root Cause

• Korean characters use 3 bytes in UTF-8 encoding
• The character '트' occupies bytes 6-9
• The code tries to slice at byte index 8, which is in the middle of '트'
• Rust panics because slicing at non-char boundaries is not allowed

Environment

• OS: Windows 11
• Claude Code CLI version: latest
• Locale: Korean

Frequency

This issue occurs frequently during normal usage, especially when:

• Working with Korean filenames
• Working in directories with Korean paths
• Processing Korean text content

Expected Behavior

The CLI should properly handle UTF-8 multibyte characters by using character boundaries instead of byte indices when truncating strings.

Suggested Fix

Use char_indices() or similar UTF-8 aware methods when truncating strings:

// Instead of: &s[..8]
// Use something like:
fn safe_truncate(s: &str, max_chars: usize) -> &str {
    match s.char_indices().nth(max_chars) {
        Some((idx, _)) => &s[..idx],
        None => s,
    }
}

Or use the unicode-segmentation crate for proper grapheme cluster handling.