v1.1.14 — Non-pickable bodies
Closes #63: ViewportBody.isPickable (default true) excludes a body from the GPU pick buffer while still drawing it, so always-on-top reference/overlay bodies (datum/ground planes) stop stealing face/edge/vertex picks. Gated in every pick sub-pass; pick IDs stay stable. PickabilityTests; 141 tests; no behaviour change by default.