[BUG] No cofirmation on left arrow press before switching to agent view

### 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?

According to https://github.com/anthropics/claude-code/issues/75899#issuecomment-5310814032

> pressing ← right after editing (e.g. you just backspaced the input empty) now asks to confirm with "Press ← again" instead of switching immediately

I don't see this behavior with 2.1.241 (Claude Code) on Ubuntu 24.04.

Pressing left arrow in an empty input area immediately enters the agent view.

See the video demonstration of the bug:

https://github.com/user-attachments/assets/013504ed-fa15-42bf-8dd9-731f4c8d1f80

### What Should Happen?

When left arrow is pressed, a confirmation dialog appears to prevent accidental entering of the agent view.

### Error Messages/Logs

```shell

```

### Steps to Reproduce

1. Restore default settings: `rm -f ~/.claude/settings.json`
2. Create a fresh directory: `mkdir /tmp/claude-agent && cd /tmp/claude-agent`
3. Lauch `claude`, trust the working dir, then press left arrow key

### Claude Model

Not sure / Multiple models

### Is this a regression?

Yes, this worked in a previous version

### 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

Despite https://github.com/anthropics/claude-code/issues/75899#issuecomment-5310814032 saying

> please reply if you still see either problem on 2.1.233+ and we'll reopen

reopening does not happen after the comment https://github.com/anthropics/claude-code/issues/75899#issuecomment-5388458845.

Therefore this issue is opened, and needs to collect at least 10 upvotes or be periodically commented on to prevent auto-closure, see https://github.com/anthropics/claude-code/issues/87647.

Reproduce the issue from a fresh directory using the documented Claude Code launch and left-arrow steps on Ubuntu/Debian Linux. Trace the terminal input handling for an empty input and verify that pressing left arrow shows the confirmation prompt before entering agent view.

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