Improve layout of smart selection actions panel
Improve cmd-click behavior to be more mac-like: a cmd-click on an inactive window/pane behaves like a non-cmd-click that doesn’t give focus. Also clean up some odds and ends with click handling: reset the selection’s appending flag when you click on an image or on the selection (relevant after creating a discontinuous selection). Don’t highlight url’s when the cursor is over an image. Restrict mouse reporting to the 'live' region at the bottom of the scrollview.