Mockup G — Imported-mesh texture replacement (UV-mapped)

What's special on imported meshes

• Acknowledgement chip beside MATERIAL heading — 🔗 UV-mapped (3 slots) — communicates "we know this is an imported mesh, not a parametric prim."
• Material preset chips greyed with explanatory copy. Clicking "Metal" on a UV-mapped tree shouldn't apply across the whole mesh because it conflicts with the imported per-slot materials.
• Per-slot TextureThumb rows — one per material slot. Each shows the slot's diffuse texture as a thumbnail with name + [Replace ▸] button.
• Color picker still applies as tint — works on UV-mapped meshes (multiplies into albedoColor); reassurance hint says so explicitly.
• One-line disclaim at the bottom — sets correct expectations about what's editable in-world vs what needs external tooling.

Detection rule

• "UV-mapped imported mesh" trigger condition: mesh.geometry.hasAttribute('uv') AND mesh has >0 slot materials in its MultiMaterial from import (not procedurally added).
• Parametric prims (Box / Sphere / Cylinder / Torus) never trigger this mode — they get the regular Mockup A LookTab.

Phase placement

• Estimated ~550 LOC. Fits inside ADR-126 phase 2 or 3 — does not require ADR-131 (the layout-editor stub).

Pending Q answers

• Q12 — §2.4 scope-clarification + future ADR-131 stub.
• Q13 — separate [Replace ▸] button vs reuse [↑] upload-icon. This mockup shows separate Replace + Clear; tech track preference still open.