An open sidebar panel (a web app or an extension panel) now has a bar on
top with its name, Maximize/Restore (it covers the page, up to the right
sidebar) and Close. How panels sit next to the page is a choice, in the
new gear above + on the strip and in Settings > Sidebar: over the page,
where it floats on the left of a page that keeps its width and a click in
the page closes it; or pushing the page aside, where it stays open until
closed. That choice replaces the pin, which only existed to keep a panel
open on a page click.
Also: a window laid out while minimized reads a zero-size area, so every
view was left at 0x0 and the window came back blank until resized.
Layout now skips a minimized window and runs again on restore.
