DetailWebView.setFrameSize() calls bigSurOffsetFix(), which changes the window's frame, which ultimately calls setFrameSize() again (which calls bigSurOffsetFix(), etc). In practice, this isn't causing an infinite loop (I think NSWindow.setFrame(_:display:) is smart enough to prevent reentrancy) but it's still dangerous to have such a glaring logic error in the code.
Move the code that twiddles the window frame from DetailWebView.viewDidEndLiveResize() into a new bigSurOffsetFix() API so it can also be called by setFrameSize() when the frame size is changed outside of a live resize.