The /context dialog scrolled as a whole while the DNA feed rode it, and
scrubbing the composition bar dragged the dialog too — the row reveal's
nearest scrollable ancestor was the dialog card itself. In the tab, the
3x left-column cap let the card outgrow the pane and change height on
every DNA toggle, dragging the head off-screen and the cards below with
it; band picks scrolled the page via scrollIntoView.
Make the card's own fixed zone the rule in every host: head, DNA lens
and block map stay put while only the rows region scrolls. The tab
column caps at the left column's height bounded by the host scrollport's
slice from the card's top edge (browserCapOf), so toggling DNA or
opening categories never moves the cards below; the /context dialog
becomes a filled flex column whose browser card shrinks instead. Row
reveals bind to the card (revealRowInCard): scrubbing and picks never
scroll above it, and the rows region contains its wheel so the page only
moves when the pointer leaves.
bowenliang123
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