[FEATURE] Add a setting to exit with a single Ctrl+D instead of pressing it twice

### Preflight Checklist

- [x] I have searched [existing requests](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20label%3Aenhancement) and this feature hasn't been requested yet
- [x] This is a single feature request (not multiple features)

### Problem Statement

[[FEATURE] Add a setting to exit with a single Ctrl+D instead of pressing it twice](https://github.com/anthropics/claude-code/issues/79453#issue-4929949979)

### Proposed Solution

https://github.com/anthropics/claude-code/issues/79453#issue-4929949979

### Alternative Solutions

_No response_

### Priority

Critical - Blocking my work

### Feature Category

CLI commands and flags

### Use Case Example

_No response_

### Additional Context

_No response_

Start by reading the linked issue #79453, which contains the proposed solution. Then locate the CLI input and exit handling and the settings entry point; done means a configurable option allows exiting with one Ctrl+D while preserving the existing default behavior.

Written by the indexing model from the issue text.