[BUG] When drag out the chat tab it looses the prompt

### Preflight Checklist

- [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) 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?

When drag out the chat tab as new window it looses the entered prompt.

Prompt is lost:

### What Should Happen?

It should preserve the typed prompt so I can continue edit and submit it. Other tabs that i open like that keep their content.

### Error Messages/Logs

```shell

```

### Steps to Reproduce

Open a new Cloude Code chat as a tab.
Type some prompt.
Drag the tab out of the window so it opens as a new window.
Claude Code opens as a new window but the prompt is deleted/empty.

### Claude Model

Sonnet (default)

### Is this a regression?

No, this never worked

### Last Working Version

_No response_

### Claude Code Version

2.1.274

### Platform

Anthropic API

### Operating System

Windows

### Terminal/Shell

Terminal.app (macOS)

### Additional Information

_No response_

Start by tracing the chat-tab drag-out and new-window flow described in the reproduction steps, then reproduce it with a typed prompt. Done means the new window retains the prompt so it can be edited and submitted.

Written by the indexing model from the issue text.