My Browser connector toggles that stay off · clearer X Article export errors

Fixed a bug where turning off a My Browser connector did nothing when two or more browsers were connected at once: the switch flipped back on immediately, because the "don't auto-enable this" preference was only remembered when every browser was switched off. Your choice is now remembered per browser, so switching one off leaves the other running.
Your switched-off browser now stays off across a reconnect or an extension reinstall, instead of quietly turning itself back on.
A browser connector that is unavailable now says so on its row, instead of showing a greyed-out switch with no explanation.

Fixed an export failure that left you looking at X's own "page not found" screen: the failed tab is now closed instead of brought to the front.
Export errors now tell you what actually went wrong — whether it is your X login or Premium status, clipboard permission, or draft verification — instead of one generic message.
When several browsers are connected, X Article export now picks the browser you are actually using instead of refusing to run.