spatial-transform

Pure, dependency-free transform math for the spatial attachment mechanics (see SPATIAL-DESIGN.md) — vector/quaternion ops plus the compose ↔ relative pair that underpins place-relative and transition (re-parent preserving world pose).

Plain {x,y,z} / {x,y,z,w} objects, no Babylon, so it unit-tests headless like fly-by-wire and terrain-grid. The Babylon bridge (reading node world matrices, setParent, floating-origin world-root flipping, the declarative elements) lives elsewhere and delegates the math here.