Pages no longer stall on "Building layout…"

Occasionally a page would connect normally and then never finish: the loading frame stayed up, nothing failed, and nothing appeared in the logs. Reloading usually fixed it, which made it look like a hiccup rather than a bug.

It was not a hiccup. Updates for one page travel from the node that owns it to your browser as a numbered sequence, and the receiving side deliberately ignores an update older than the one it already applied — that is what stops a delayed message from undoing newer state. The distributed router, however, was sending those updates on independent threads, so two of them could swap places on the way. When the swap happened to hop over the update carrying the page's actual content, that content was ignored as "old" and never sent again: the page kept the loading frame it started with, forever.

Updates for the same destination are now sent strictly in the order they were produced, so the page always receives its content.