ConstThe navigator's current annotation draws last (on top) at full strength; the others dim. That is
what keeps overlapping annotations legible. Annotations that share a top-left cell share one chip —
the current one's if it is among them — with a +N for the rest, so chips never stack.
A prebuilt layer, not part of the sheet's default stack: a host that shows annotations injects it
through the sheet's layers (propsSheet={{ layers: [<RangeAnnotationLayer key="annotations" />] }}
on a workbook element). It reads the sheet from context and draws nothing while the workbook has no
annotations. Fed through addRangeAnnotations.
The workbook's range annotations on this sheet: a soft box per annotation, and a chip per anchor cell. The chip rides a StickyPortal with
whenOff: 'clamp', so when its range scrolls out of view it stays at the edge as a small marker (the position, an arrow toward the range; click reveals it) instead of vanishing.