[BUG] Windows Terminal: Ctrl+C on selection containing CJK triggers interrupt instead of copy

Environment

• Claude Code version: 2.1.101
• OS: Windows 11 (Build 26200)
• Terminal: Windows Terminal
• Shell: bash (Git Bash) / PowerShell 7

Description

When Claude Code output contains CJK characters (e.g., Traditional Chinese), selecting text and pressing Ctrl+C is treated as app:interrupt instead of copy selection. This force-exits the current turn, requiring claude --resume to recover the session.

Pure-ASCII selections in the same session copy correctly via Ctrl+C.

Expected Behavior

Per docs (https://code.claude.com/docs/en/fullscreen):

If you have a selection active, Ctrl+c copies instead of cancelling.

Ctrl+C on any active selection — CJK or not — should copy.

Actual Behavior

• Selection containing CJK → Ctrl+C interrupts the turn, selection detection fails
• Selection with only ASCII → Ctrl+C copies correctly
• Session must be recovered with claude --resume

Steps to Reproduce

1. Start Claude Code in Windows Terminal
2. Ask a question that produces a response containing Chinese/Japanese/Korean
3. Select a region of the output that includes any CJK character
4. Press Ctrl+C
5. Observe: turn is interrupted; clipboard not updated

Hypothesis

Selection-detection logic likely uses byte-width or cell-width assumptions that mis-handle CJK wide characters, causing the TUI to conclude "no active selection" and fall through to app:interrupt.

Related Issues

• #42538 — Korean text mojibake when copied from Windows Terminal (CJK + copy family)
• #43477 — Ctrl+C copy fails in VS Code on Windows
• #43364 — Docs confirm Ctrl+C on selection should copy

Workaround

Right-click copy or Windows Terminal's "Automatically copy selection to clipboard" setting both bypass the issue.