[Bug] Panic on UTF-8 char boundary with Korean text during editing

Bug Description
thread '<unnamed>' (171697414) panicked at /rustc/ed61e7d7e242494fb7057f2657300d9e77bb4fcb/library/core/src/str/mod.rs:833:21:
byte index 2 is not a char boundary; it is inside '지' (bytes 0..3) of 지==.
note: run with RUST_BACKTRACE=1 environment variable to display a backtrace
fatal runtime error: failed to initiate panic, error 5, aborting
[1] 81621 abort claude --dangerously-skip-permissions

This keep poping and cuase fault when editing Korean. Please fix this.

Environment Info

• Platform: darwin
• Terminal: tmux
• Version: 2.0.71
• Feedback ID: e92d6a8c-9c90-4451-a672-e870985bd50f

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/jacey/.local/share/claude/versions/2.0.71 (expected in multi-process scenarios)\n    at hXR (/$bunfs/root/claude:2415:2165)\n    at JKA (/$bunfs/root/claude:2415:1885)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-12-19T03:02:46.253Z"}]