Two layout defects in the Knowledge Base modal, both found during
v1.34.0-rc.4 QA.
The collection combobox list was clipped to a single row's height on
every row of the table. The cause is not stacking order - StyledTable
gives each cell `truncate` (overflow:hidden) plus `relative`, so an
absolutely-positioned child cannot escape the cell box. No z-index can
win against a clip. The modal body is also an `overflow-y-auto`
scroller, so simply opting the cell out of `truncate` still left rows
lower down clipped by the scroller instead.
Render the list in a portal with fixed positioning instead, measured
from the input's rect and flipped above when it would run off the
bottom of the viewport. Reposition on scroll and resize (capture
listener, so any ancestor scroller counts). The click-outside handler
now also checks the portaled list, otherwise mousedown on an option
would close it before the click landed.
Separately, the modal was capped at max-w-4xl (896px) while its table
needs 906px, so the Delete button lost its right edge for everyone
regardless of monitor size. max-w-5xl gives the table room with none to
spare wasted.
Verified against a real build on a test appliance.
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