Two bugs hid the popup that opens on double-click (or right-click) of
a GPU button in the Serve panel:
1. z-index 240 vs the cookbook modal at 260 — popup rendered behind
the modal it was spawned from.
2. Horizontal position was just `button.left`, with no clamp against
the viewport. GPU buttons sit near the right edge of the modal, so
the popup got anchored at a left that pushed most of its body past
the viewport's right edge.
Switch the popup to position:fixed (escapes scrolling / transform
stacking contexts on any ancestor), bump z-index to 10010 (above the
themed-confirm / overlay layer that sits around 9000-10000), and
clamp left/top after measuring the rendered size — including flipping
above the button if there isn't room below. The popup is now fully
visible regardless of which GPU button it's anchored to or how
narrow the viewport is.
853576273a