On upg-100-mfe at phone width the map pane is stacked (position:absolute; inset:0) BEHIND Prayer Resources,
so the IntersectionObserver, which measures geometry and not occlusion, still reported the map as in view
and the pill floated over the posters (the Driver's report; flagged by repo before the README retake).
The contract: a composite marks an inactive view inert (or hidden / aria-hidden="true"), which is also what
assistive technology needs. The pill hides while any ancestor of its map carries one of those, walking up
through shadow roots, and a MutationObserver on that chain brings it back when the reader picks the map.
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