Omaframe 0.7.4: window scrollshots

Scrolling capture now works on windows only. Press S in the selector, then
click the window you want. Dragging an area or pressing F no longer starts a
scrolling capture, since small areas gave the stitcher too little overlap and
often fell back to scrolling by hand.

To keep only part of a page, crop the result in the editor.

Install or update with the attached omaframe-x86_64.pkg.tar.zst package,
then reopen Omaframe. Existing settings, captures and drafts are preserved.

Tested with all eleven suites in an isolated Omarchy desktop, the Chromium
scrolling smoke, and hands-on selector checks for clicks and drags.