[BUG] Windows desktop: pop-out control for the artifact/preview pane is missing, pane can no longer be detached into its own window

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?

In the Code tab of the Windows desktop app, the artifact/preview side pane can no longer be popped out into its own window. The pane header used to have an icon for this, and I used it daily on a two-monitor setup. It is gone: the header now shows only the title dropdown, the comments button, Share, expand and close (screenshot below).

What I tried, none of which detaches the pane:

• dragging the pane header outside the main window
• the dropdown next to the pane title
• the Views menu in the session toolbar
• Help → Check for Updates

The desktop docs still describe this ("pop a pane such as the diff or terminal out into its own window, and dock it back when you're done"), so I don't think it was removed on purpose.

Possibly related: #97382 (popped-out artifact window closes on republish, Windows, since the Sept 24 update) and #90424 (pop-out state stuck in session-popouts.json).

What Should Happen?

The pane header offers a way to pop the pane out into a separate window, as before.

Error Messages/Logs

Steps to Reproduce

1. In a Code tab session, have Claude publish an artifact with the Artifact tool.
2. The artifact opens in the side pane.
3. Look for a way to pop the pane out into its own window.

Claude Model

_No response_

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude Code 2.1.281, Claude for Windows desktop app 2.16120.0 (801c07)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_