RE-15-08: Decode real wall compound-layer thicknesses and wire to IfcMaterialLayerSetUsage

[DrunkOnJava]

Problem

v0.2.0 emits IFCMATERIAL and IFCWALL entities but does not
associate walls with their compound-layer structure. Revit
walls have a WallType referencing a CompoundStructure with
layered materials + thicknesses; v0.2.0 drops this data.

Refs: ROADMAP CLASS-07 (compound layers); CHANGELOG [0.2.0]
(no wall-material associations).

Scope

• Decode WallType.CompoundStructure from partition bytes.
• Build IfcMaterialLayerSet (one per WallType).
• Emit IfcMaterialLayerSetUsage + IfcRelAssociatesMaterial per
  wall instance.

Acceptance criteria

• At least 5 distinct IfcMaterialLayerSet entities in
  2024_Core_Interior.rvt IFC export.
• Each wall has a RelAssociatesMaterial pointing to its
  LayerSetUsage.
• Layer thicknesses round-trip from Revit-bytes within
  tolerance (track per-fixture).

Related

• Umbrella: M4-06: Recover materials and compound assemblies #34 (M4-06 Recover materials and compound assemblies)