The first version of quick compose skipped `onBeforeCompose`, a composer
moved back could end up open in both windows, a reply moved back under
Pro flagged the selected message, and a crashed pop-out came back blank.
- A new message in a pop-out runs `onBeforeCompose` with the same result
as the main window: a plugin that stops it closes the window.
- The way back has two steps, so a pop-out that gave up can't leave a
second owner. A handoff behind a plugin's gate makes it say busy.
- A Pro tab made from a composer moved back answers its own message.
- Each save writes `draft`, `account` and `owner` into the pop-out's
address, which a reload after a crash starts from. What was typed since
the last save, up to the 2 s autosave delay, is still lost.
- The recorder refuses keys that type a character on this keyboard, and
what the shell refuses from a page, and says why.
Linus Rath
71aaadef50