fix: clean up empty file after failed wl-paste clipboard extraction

When wl-paste produces empty output, the destination file was left
on disk as a 0-byte orphan. Now explicitly removed before returning
False.

hermes_cli/clipboard.py

@@ -254,6 +254,7 @@ def _wayland_save(dest: Path) -> bool:
             )
 
         if not dest.exists() or dest.stat().st_size == 0:
+            dest.unlink(missing_ok=True)
             return False
 
         # BMP needs conversion to PNG (common in WSLg where only BMP