[BUG] Regression in 2.1.7: Rust panic on UTF-8 emoji (✅) in file content

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Description

After upgrading to Claude Code 2.1.7, the CLI crashes with a Rust panic when reading or displaying files containing UTF-8 emojis (specifically ✅).

## Error Message
thread '' (21718640) panicked at /rustc/ed61e7d7e242494fb7057f2657300d9e77bb4fcb/library/core/src/str/mod.rs:833:21:
byte index 2 is not a char boundary; it is inside '✅' (bytes 0..3) of ✅
fatal runtime error: failed to initiate panic, error 5, aborting
zsh: abort claude

## Reproduction

1. Create a file with ✅ emoji (e.g., TASK_CHECKPOINT.md)
2. Use Read tool or cat the file in Claude Code
3. CLI crashes with above error

## Environment

• Version: 2.1.7
• Platform: macOS 24.6.0 (Darwin)
• Previous version: Worked fine before upgrade
• This is a regression - emoji handling worked in previous version

## Impact
Crash causes loss of conversation context and interrupts workflow.

What Should Happen?

It should continue to allow the ✅ emoji without crashing

Error Messages/Logs

Steps to Reproduce

put a ✅ emoji in a .md file and use it as instructions

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.7

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_