Falls back to the bare label when the node authored no copy template, so
every labelled layer gets a working Copy with no authoring at all. Not
escaped — plain text destined for the clipboard is exactly what was asked
for — but length-capped, because it outlives the page.
Build the copy string, or null if there is none.
Falls back to the bare label when the node authored no
copytemplate, so every labelled layer gets a workingCopywith no authoring at all. Not escaped — plain text destined for the clipboard is exactly what was asked for — but length-capped, because it outlives the page.