Plugin Studio read its tab from #<bundle/profile> or from localStorage, and
never wrote it, so a reload worked for one reader but a sent link did not. It
now writes the view address through useViewAddress: ?tab=<bundle>__<profile>
(a row key's "/" is not a plain id; the double underscore keeps a sent link
meaning one row even if another bundle later adopts the profile's name). A
reader's tab click is a push, the first paint a replace, and Back/Forward
re-open the named tab without writing. route() reads ?tab= first (or a bare
profile name while it names exactly one row), then the old #bundle/profile
(rewritten to ?tab= on first paint, its hash dropped), then the remembered
tab, then the first row. The listener is removed before the hot-update return.
generate-tree bakes urlOwner 'app' into our own leaf pages only (never into an
embed snippet), and a framed leaf drops it at runtime, so a page embedded in a
partner's iframe reads its address but never adds entries to the partner's
Back button.