This function calculates metrics at the "landscape" level, filtering for
"complexity metric" types. The function prioritizes data integrity by
adding a temporary plot_id column based on row index, which is used
by landscapemetrics.
Crucially, the function uses dplyr::left_join with this plot_id
for merging the results. This **robust join method** prevents data misalignment
that could occur if rows were dropped during metric calculation, which is a significant
improvement over the unsafe cbind method. The temporary plot_id column
is removed before the final object is returned.