CLASS-14: Beam / StructuralFraming decoder + IfcBeam / IfcMember emission

[DrunkOnJava]

Problem

Structural framing (beams, joists, braces) is not decoded.
Columns shipped at 100% recall in v0.2.0 (256/256) so the
structural class path is partially proven; beams are the
next logical add since they share the FamilyInstance-with-
curve-path layout.

Scope

• Decode StructuralFraming records — profile + curve path
  (start/end + curve type).
• Emit IFCBEAM (or IFCMEMBER for braces) with IfcSweptSolid
  along the path.
• Material association via profile (IfcMaterialProfileSet).

Acceptance criteria

• Beams emitted on at least one structural corpus fixture
  when added.
• Profile shapes (I-beam, rectangular, tubular) covered for
  top 5 common cases.
• Diagnostics for unsupported profiles.

Related

• Per TODO-BLINDSIDE Phase 4 L5B-29
• Parallels column path proven in v0.2.0