A container's own visible card is inset from its allocated board cell
by the board's standard per-item gap, but items inside it are
positioned in a coordinate space sized to the un-inset column/row
count - so without correcting for that, items (not just the grid's
own box) spilled past the container's right/bottom edge by that
inset amount, worse the busier/more zoomed-out the board is.
Scales the container's inner grid content down to fit the actual card
size, using the same zoom mechanism the board's own top-level canvas
uses for its whole-board zoom, just one level deeper. Corrects
--board-canvas-ui-scale to compensate so icon/text/custom-CSS sizing
inside the container isn't affected - computed as a plain JS number
rather than a CSS calc() referencing the property's own inherited
value, since custom properties don't have a sequential/temporal order
within the same element and doing so is a circular reference that
silently invalidates the whole property for every descendant.
Also fixes the collapsible container's label bar poking above the
card's rounded top border via a negative offset - it now sits flush
inside it.
Bergasha
78a4f0e513