A reveal on a deep tree shifted the whole panel (tab bar included) out
of the viewport: the reveal used native scrollIntoView, which scrolls
every scrollable ancestor, and the fixed panel host
([data-dsh-panel-host], overflow hidden) is still a programmatically
scrollable container — the host scrolled instead of (or besides) the
tree, with no way to scroll back. Reported on DSH 0.1.2-alpha.1.
Two layers:
- FileTree: compute the centered, clamped target and scrollTo the tree
body only; scrollIntoView is never called.
- panel host: overflow hidden -> clip. A hidden box remains
programmatically scrollable; clip keeps the same viewport-edge
clipping (collapsed panels sliding off-screen) while making the host
impossible to scroll, killing the whole leak class (md-toc jumps,
future consumer scrollIntoView calls).
