[BUG] File preview in Claude Desktop is unnecessarily thin. (Small)

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?

The file preview area has recently shrunk horizontally. Previously the width was suitable for reading files, now it's compressed to a thin vertical strip similar to that of a phone screen. Lines are forced to wrap and the reading experience has degraded.

<img width="3440" height="1392" alt="Image" src="https://github.com/user-attachments/assets/d5099742-d633-41f9-9098-a364ecdde2bb" />

What Should Happen?

The preview area should revert back to the previous width, or better yet, make use of the available space the user defines when sliding the resize partition handle around.

Error Messages/Logs

None. It's UI

Steps to Reproduce

Create a .md file with Claude Code and in the working directory and open it in the Files viewer.
This issue may be in a non claude code chat too.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.287 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

I'm not using a terminal, there was no option for "None". This is the Claude Desktop app.