Strict, codec-independent IFC presentation and annotation views.
Appearance stays separate from geometry: this crate exposes colour, style,
texture, layer, styled-item, and annotation semantics over ifc_model::Model
without placing presentation state in the geometry kernel. Reads and writes
resolve attribute slots through the selected ifc_schema::Schema, so IFC2x3,
IFC4, and IFC4X3 layout drift is explicit rather than guessed.