Deciding where a piece of page state lives comes up in review after
review, and the answer only holds if everyone reaches the same one. Write
it down: what the address bar is for, what belongs in a component or a
query instead, and the traps worth knowing before the second page adopts
this.
The page opens doc/ui/guidelines, an index meant to become the single
place to look for interface conventions. The ones written earlier stay
where they are for now and are listed there, so nothing is lost while
they move over one at a time.
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