Add paste image from Mac to linux wayland

[heavysink]

For now, cocoa-way does not support pasting image via wayland. I tried to create the patch so that pasting image via shell is possible. It is helpful for remote codex session.

[J-x-Z]

Thanks for working on macOS-to-Wayland image clipboard support is useful,
and I would like to merge the feature after a few issues are addressed。

---

1. NSData should use data.to_vec() rather than
   data.bytes().to_vec().

---

2. poll_host_clipboard() currently calls pasteboard_snapshot() before
   checking whether changeCount changed. Since the snapshot may decode TIFF
   and encode PNG, this can repeat expensive image conversion every 100 ms
   while the clipboard is unchanged. Please check changeCount first and only
   read/convert the image when it changes.

---

3. Please avoid cloning the complete PNG for every Wayland request. Storing it
   as Arc<[u8]> and adding a reasonable maximum clipboard image size would
   prevent large memory spikes.

Please also confirm that text clipboard behavior, clipboard clearing, and pasting a macOS screenshot into a Wayland application have been tested.