nx_assembly.nx

nx_assembly.nx -- LIB: GENERAL hierarchical PRODUCT digital twin -- the LibrePCB/BOM capability scaled all the way up from a PCB to a whole product (a fridge, a car). A product is an ASSEMBLY TREE: nodes are sub-assemblies or real parts (leaves); each leaf carries real supply-chain data (unit cost cents, mass grams, stock). Rollup computes EXACT integer totals (cost, mass, part count) and supply-chain shortfalls over the whole tree -- the real "what it costs / weighs / can we source it" of the product, hardware-rung-up. Sub-assemblies compose lower twins (e.g. the control board = the nx_bom PCB twin). Data-driven: a new product = a new node table. never-brick #26: pure arithmetic, bounded, deterministic. license_tier: ORIGINAL