v1.3: Upgrade quality and efficiency (#14)

feat: surface topology classification, per-part color/RGBA recipes, Tier-1 diagnostics, hash caching, real extrude/lathe/tube geometry

Implements Plan 1.3 (schemaVersion 2.1): topology-gated primitive selection, CIE Lab color+gradient extraction with RGBA output, silhouette/proportion/symmetry pre-checks before AI-vision review, PBR material completeness (env map, ior/sheen/iridescence/anisotropy), and content-hash caching for extraction scripts.

Merge pull request #9 from hoainho/refactor/stage-prefixed-script-names

refactor: restructure project layout ahead of the full harness rebuild