v0.15.0 — rigged assets cast shadows, website camera feel

Fixed

• Rigged assets cast no shadow. The shark had none, the sea anemone did, and the difference was the rig: the planar shadow walked MeshRenderer, and a rigged asset draws through a SkinnedMeshRenderer — a Renderer, but not a MeshRenderer. Every character and fish was skipped.
• The same blind spot leaked a mesh per rebuild on those assets.

Changed

• The preview camera moves like the one on polyfork.dev. viewer.js runs OrbitControls with enableDamping; this moved instantly and stopped dead. Input now sets a target the camera eases towards, repainting only while it glides. A drag of the preview's full height is one revolution, as OrbitControls does it. Zoom clamps to 0.35x–2.5x the framing distance, matching minDistance/maxDistance in viewer.js.