[BUG] Don't render content that is not Markdown as Markdown (i.e. don't interpret `_`, `*`, etc. as Markdown tokens)

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?

See the attached screenshot. Due to presence of _ in the justfile, some text is incorrectly rendered as italic:

<img width="929" height="272" alt="Image" src="https://github.com/user-attachments/assets/2364a373-db25-41e4-9a70-815ae3019d8f" />

What Should Happen?

Only Markdown content should be rendered/interpreted as Markdown.

Error Messages/Logs

Steps to Reproduce

Ask Claude Code "Write a production-ready, best-practices Justfile with two recipes foo-bar and lorem-ipsum".

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.0.55

Platform

Anthropic API

Operating System

Other Linux

Terminal/Shell

Other

Additional Information

_No response_