[css-grid-2] Clarify duplicate line name resolution in grid-template-areas

[gitspeaks]

In section 7.3.2, it states:

These implicitly-assigned line names behave just like any other line names, except that they do not appear in the value of grid-template-rows/grid-template-columns. Even if an explicitly-assigned line name with the same name is defined, the implicitly-assigned line names are just more lines with the same name.

This implies that implicit line names (e.g., “foo-start” from grid-template-areas: "foo foo" "bar bar") and explicit line names (e.g., “foo-start” from grid-template-rows: 100px [foo-start] 200px) coexist as separate lines, even with the same name. However, it’s unclear how the grid resolves a reference like grid-row-start: foo-start when multiple lines share the name “foo-start.” Does it default to the first occurrence ?

[fantasai]

Does it default to the first occurrence ?

Yes. See https://www.w3.org/TR/css-grid-1/#line-placement

<custom-ident>
First attempt to match the grid area’s edge to a named grid area...

Otherwise, treat this as if the integer 1 had been specified along with the <custom-ident>.