GABRB3 and Alzheimer disease: Multiscale coexpression mapping resolves three disease clusters: a neuron-mitochondrial module suppressed in AD (M5; hub PJA2; key driver GABRB3), a microglial immune module upregulated in AD (M6; hub C1QC; key driver FCER1G), and an increased astrocyte-vascular extracellular-matrix module in AD (M8; hub ESAM; key driver TAGLN).