[BUG] Stale TUI frame remains on screen after /exit until `clear`/`reset` (Konsole, xterm-256color)

### 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?

After running exit in the Claude Code CLI, the TUI's rendered screen stays visible and unresponsive to input, even though no claude process is still running. Running clear or reset in the terminal immediately fixes it, suggesting the alternate-screen-buffer restore sequence isn't being sent/processed on exit.

### What Should Happen?

Terminal should return cleanly to the normal shell prompt on exit, with no leftover frame.

### Error Messages/Logs

```shell

```

### Steps to Reproduce

a. Run claude in Konsole
b. Interact normally, then run /exit
c. Observe the CLI's screen/UI remains rendered and inert
d. Run clear (or reset) — screen clears to normal prompt

### Claude Model

None

### Is this a regression?

I don't know

### Last Working Version

_No response_

### Claude Code Version

2.1.241 (Claude Code)

### Platform

Anthropic API

### Operating System

Ubuntu/Debian Linux

### Terminal/Shell

Xterm

### Additional Information

_No response_

No source file or test is named in the report. Reproduce the exit flow in Konsole with xterm-256color, then trace the CLI exit path and terminal cleanup behavior; done means /exit restores the normal shell prompt without a stale, inert frame and clear or reset is no longer needed.

Written by the indexing model from the issue text.