shift fix) — but as a BARE declaration. Engines without clip support
(Safari < 16, older Chromium) drop an unsupported declaration at parse
time, which leaves the host `overflow: visible`: no clipping at all,
and the historical "collapsed panels extend the document's scrollable
area, whole page draggable" regression returns on those engines.
Declare `overflow: hidden` BEFORE `overflow: clip`: clip-aware engines
apply the later clip (identical behavior to #453), while old engines
fall back to hidden and keep clipping (with its pre-clip
scrollability — the same state they had before #453, strictly better
than visible). The cascade order is the contract.
Also extends the rule comment (the fix guards the whole
scroll-into-view class — focus moving into off-viewport regions,
nested iframes/workbenches claiming focus while loading — not just the
reveal case) and adds tests/panel-host-css.spec.ts guarding the
cascade (hidden first, clip last), the fixed viewport layer, and that
the degraded rule never reintroduces overflow. Contract documented in
the integration guide §12 (root anchor bullet).
chendefine
96650fa189