gpui_linux: Add wl_data_source support for outbound drags on Wayland (#61947)

# Objective

- Enable drag'n'drop from Zed in Wayland.
- Partially addresses #13186
- Related to #58161, #61940

## Solution

- Implement wl_data_source support for outbound drags on Wayland

## Testing

Tested on KDE Wayland, kwin 6.7.3
I dragged files to Firefox, to other Zed windows and into Dolphin.  

## Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

## Showcase

Can try to record if requested

Release Notes:

- Added support for dragging files from the Project Panel to external
Linux Wayland apps.
c7aea6cbbdErik W committed on 7/31/2026, 10:29:47 AM· committed by GitHubparent56cf49b
3 files changedLine totals unavailable