Use our canonical constants in SpatialCoordsRemapper instead of lowercase substring matching

[erogluorhan]

Version

v2026.07.0

How did you install UXarray?

Source

What happened?

Nothing happened, but I just noticed a small fragility worth fixing in SpatialCoordsRemapper: _get_element_type_from_dimension does lowercase substring matching ("face" in dim_lower) to guess element type, but uxarray/conventions/ugrid.py already defines canonical NODE_DIM, FACE_DIM, EDGE_DIM constants that internal dimension names always match exactly.

What did you expect to happen?

Use constants instead of substring matching.

Can you provide a MCVE to repoduce the bug?

[Sevans711]

(Flagging as possibly related: #1574)