[FEATURE] Allow Ctrl+D, Ctrl+D to exit claude agents (consistent with claude --resume)

### 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

https://github.com/anthropics/claude-code/issues/79451#issue-4929888766

### Proposed Solution

https://github.com/anthropics/claude-code/issues/79451#issue-4929888766

### 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 linked issue #79451 and tracing the existing `claude --resume` Ctrl+D behavior; the issue names no source file or test. Done means the requested Ctrl+D, Ctrl+D exit behavior for claude agents is implemented consistently with `claude --resume` and verified in the CLI.

Written by the indexing model from the issue text.