TUI misalignment caused by string-width miscalculating emoji character width on macOS 12

Bug

Claude Code's TUI output is misaligned on macOS 12. Two symptoms:

1. Main output: The bullet emoji ⏺ (U+23FA) before each task item causes all subsequent text on the same line to be offset
2. Status line: Emoji characters in the status bar render as garbled/misaligned text

Root cause: the internal string-width treats ⏺ as 1 cell wide, but the terminal actually renders it as 2 cells wide.

Environment

• macOS 12.7.6 (Monterey)
• iTerm2 3.6.8
• Claude Code 2.1.63
• System ICU: 70.1 (libicucore.A.dylib)
• Terminal: xterm-256color, locale en_US.UTF-8

Root Cause Analysis

• Claude Code (Bun binary) links against /usr/lib/libicucore.A.dylib (ICU 70 on macOS 12)
• System wcwidth(0x23FA) returns 1, but iTerm2 renders ⏺ as 2 cells wide
• The ambiguousIsNarrow option in string-width is likely defaulting to true, causing the mismatch
• Does not reproduce on newer macOS versions (13+) with ICU 72+

Suggested Fix

1. Pass { ambiguousIsNarrow: false } to string-width, or auto-detect based on terminal/OS environment
2. Alternatively, provide a --no-emoji or --ascii flag to replace emoji indicators with plain ASCII characters

Reproduction

echo "X⏺X"
echo "XXX"
# Second X in first line is offset from third X in second line