The tooltip clamped its centre to a fixed 92px margin, but the caption is up to 240px wide
(120px half), so a left-edge anchor (e.g. the nav-rail counts icon at x~40) pushed the centred box
~28px off the left of the viewport. Clamp with the caption's max half-width so it can't overflow on
first paint, then a useLayoutEffect re-centres on the anchor using its actual width. Verified: the
nav-rail counts tooltip now sits fully on-screen.
peter
0ad0ba6cfe