Function stampOrderedSelectors

Emits one selector per element, in the order given, by stamping each with a MAIDR-owned index attribute.

For the traces whose payload order is the binder's own rather than the DOM's — a gantt nests its intervals by lane, a hexbin its bins by lattice row — a single selector matching every mark is worse than no selector at all: it resolves in DOM order, so the model pairs each announced datum with whatever mark sat at that position, and the counts still match so nothing detects it.

The stamp is an attribute the binder owns rather than a structural :nth-child(N), which any later DOM insertion would shift, and every stamp already under the root is cleared before the new ones are laid down so rebinding after a D3 data update leaves a clean state.