Add primary clipboard support for clipboard history and enable pasting to terminals

### Feature Description

Add an option to support using the primary clipboard so that any copy actions additionally go to the primary clipboard. Pasting with `ctrl+v` is inconsistent between terminals and desktop applications, but pasting with `shift+ins` from the primary clipboard can be.

### Use Case

Pasting form the clipboard history using "shift+enter" into a terminal.

### Compositor(s)

All compositors

### If Other, please specify

_No response_

### Proposed Solution

If the primary clipboard option is enabled, when pasting from clipboard history using "shift+enter" should copy the item to both the Wayland and primary clipboards, and send the keys "shift+ins" to paste form the primary clipboard.

### Alternatives/Existing Solutions

_No response_

No files or tests are identified in the issue. Start by locating the clipboard-history handling for Shift+Enter and the terminal paste path, then trace how Wayland and primary clipboards are written and how compositor key events are sent. Done means the option copies to both clipboards and terminal pasting sends Shift+Insert without breaking desktop pasting.

Written by the indexing model from the issue text.