Right-click paste in "Plan Ready for Review" prompt pastes into previous input instead

### Describe the bug

When in Plan mode, at the "Plan Ready for Review" prompt, pasting text via right-click into the "Suggest changes" input field does not work. The pasted content does not appear in the current input. Instead, after exiting Plan mode, the pasted content appears in the previous input field.

### Affected version

1.0.21

### Steps to reproduce the behavior

1. Start a session in Plan mode using Git Bash
2. Wait until the plan is generated and the "Plan Ready for Review" prompt appears
3. Copy some text to the clipboard
4. Right-click in the "Suggest changes" input field to paste (Git Bash pastes clipboard content on right-click by default)
5. Observe that nothing is pasted into the current input
6. Exit Plan mode
7. Observe that the pasted content now appears in the previous input field

### Expected behavior

Pasted text should be inserted into the currently focused "Suggest changes" input field at the "Plan Ready for Review" prompt.

### Additional context

OS: Windows 11
Terminal: Git Bash (right-click = paste)
Copilot CLI version: (1.0.21)

Reproduce the issue in Plan mode on Windows 11 with Git Bash and inspect the implementation of the "Plan Ready for Review" prompt and its "Suggest changes" input. Trace how right-click paste is routed between the current and previous inputs. Done means pasted text appears in the currently focused input without appearing in the previous one after leaving Plan mode.

索引モデルが issue の本文から書いたものです。