Solaris / USD - traps and house rules

Staged by the 2026-11-08 round-2 baseline eval (ClaudeCode/evals/houdini-round2/ANALYSIS.md): with only the Houdini MCP the model passed both Solaris cases 4/4 (spot-light cone angle, single-sided disk light); the skill was never opened. The USD primer (layers, variants, composition arcs, LOP node reference) is cut as general know-how. What stays is what the house measured. Karma light facts come from reference/karma_lights.md.

Use the MCP first: create_lop_node, get_stage_info, get_usd_prim, get_usd_attribute, get_usd_composition, inspect_usd_layer, set_usd_attribute.

Traps (details and code in reference/)