[Bug] Panic on multibyte UTF-8 character boundary in string processing

Bug Description
thread '<unnamed>' (299462) panicked at /rustc/ed61e7d7e242494fb7057f2657300d9e77bb4fcb/library/core/src/str/mod.rs:833:21:
byte index 44 is not a char boundary; it is inside '忘' (bytes 42..45) of 控体内真气强弱，第五层过目不忘
note: run with RUST_BACKTRACE=1 environment variable to display a backtrace
fatal runtime error: failed to initiate panic, error 5, aborting
Aborted (core dumped)

Environment Info

• Platform: linux
• Terminal: windows-terminal
• Version: 2.0.73
• Feedback ID: 761efc69-f309-49d6-9065-85c53e432dad

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for *****/.local/share/claude/versions/2.0.73 (expected in multi-process scenarios)\n    at TY$ (/$bunfs/root/claude:2470:2165)\n    at D_A (/$bunfs/root/claude:2470:1885)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-12-19T18:30:08.475Z"}]