Normalise KSSL USDA subgroup labels for benchmark comparison

KSSL stores `samp_taxsubgrp` in lower-case, space-separated form ("typic hapludalfs", "aquic argiudolls"). soilKey's `classify_usda()` returns Title Case names ("Typic Hapludalfs"). The benchmark runner at `level = "subgroup"` lowercases both sides and trims whitespace, but this helper makes the normalisation explicit when users want to compare KSSL labels against arbitrary classifier output. Idempotent.

Usage

normalise_kssl_subgroup(x)

Arguments

x

Character vector of KSSL subgroup names.

Value

Lowercase, single-space-separated vector.