ascent - Multi-Layer Decomposition of Functional Community Restructuring

Implements the 'ASC-CFD' (Assemblage Shift Characterization - Community Functional Dynamics) framework for decomposing functional community restructuring into positional (centroid displacement), dispersive (functional dispersion), and boundary (convex hull volume) components. Tests each component against two null models: a sampling null model (individuals or replicates reassigned between communities) and a stratified trait-permutation null model, with a single global test when many communities are compared. Functional entities (species with similar traits) help detect replacement among similar species, and species-level leverage identifies the taxa driving functional shifts. Supports both temporal (paired) and spatial (pairwise) comparisons.