Move header flag click logic to the lineup & and add a small tweak

This pull request implements some new logic that happens when switching origin by clicking on the flag of a remote page. If the page to the immediate left is not remote, it will be opened as a remote page when the origin changes.

It could be a mistake to add something this complicated. Or it could be something we come to love.

This does showcase the lineup as a place for model logic.

This pull request includes a temporary fix. Async processing of page loads can confuse the lineup. When this happens we detect it and make things right.