On mount the map centred its active tab with
btn.scrollIntoView({ inline: 'center', block: 'nearest', behavior: 'smooth' })
and 'nearest' does not mean "do not scroll the page". It means "scroll every
scrollable ancestor by the least amount needed", and on a partner page the HOST
is an ancestor. Measured by the embed sweep: a page carrying this map below the
fold jumps to y≈640 the moment it mounts — on a phone, where Simple Research is
the default tab. The reader asked for nothing and the page moved under them.
The tab strip now scrolls ITSELF: compute the offset that centres the active
button inside its own box, clamp it to the strip's own scroll range, and write
scrollLeft. Same shape as SemanticTreeLegend's bringRowToTop, which scrolls the
container it found rather than asking the platform to walk ancestors. An element
that only ever writes its own scrollLeft cannot move anybody's page.
The exemption goes in the SAME commit, per that gate's contract — main never
carries a stale exemption or a red gate on someone else's bug. Both
NEIGHBOUR_KNOWN entries (research-map, research-map-plus-grid) are deleted here.
MEASURED after, with the exemption gone: check:gallery-embed PASS, and the
neighbour phase now reports "research-map leaves the host page alone" and
"research-map-plus-grid leaves the host page alone" on its own evidence — js 13
tabs, iframe 13 tabs, neighbour 13 tabs. The two KNOWN lines still printed belong
to regions-dashboard and are theirs to clear.
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