Stable pick key. Both meshes and items synthesize it as ${sourceComponentId}:${originalIndex}.
Layer path for grouping in the scene manager (e.g. "Structure/Walls").
OptionalmetadataArbitrary key-value pairs from the GH Metadata input.
Human label (e.g. "North wall"). Distinct from id — renaming must not change identity.
Identity + tagging shared by every display thing — meshes (via an adapter over
MeshMetadata) and items alike — so pick / filter / label code treats them uniformly. Deliberately excludes rendering concerns (color/material): those differ by kind and are not identity.