LYRW files describe themselves completely

LYRW v2 is the layer-weight file: a 24-byte header, bank descriptors, segment descriptors, one region schema per bank (experts are homogeneous, so layout is declared once), and an entry table of offsets and lengths. A reader needs nothing but the bytes in front of it, unknown tags are preserved rather than fatal, and refusal waits for the operation that actually needs what a reader cannot do.