Materials, 3D and backgrounds: inflated banding, globe arcs over time, layout-surface orientation, halo interpolation, box-shadow under transparent boxes

To do

inflated material (material: an "inflated" preset whose shading follows the clipped silhouette #385): stair-stepped bands along the inner bevel from bevel ≥ 24, and an aliased light/shade line on pills.
dot_map arcs cannot draw in over time (Project flat content in 3D: children on a curved surface, and an orthographic dot_map globe #387): draw_in is static; a draw_progress keyframe on dot_map validates and does nothing.
layout-surface cells are moved but not turned (Project flat content in 3D: children on a curved surface, and an orthographic dot_map globe #387): on a cylinder or sphere, cells are translated and depth-scaled but never rotated to face along the surface, so edge cells don't narrow or taper and neighbours overlap. Repro: a 9-column grid, 1800 wide, layout-surface: {kind: "cylinder", radius: 900, arc_x: 120}; the edge cell measures 200 px like the centre one (expected ≈120 px).
Halo zones don't interpolate between scenes (Let elements build up across beats, plus rendering gaps found reproducing an agency promo #344/fix(background): halo zones can be wide ellipses, not just circles #351): lerp_zones is dead code and background.transition cross-fades, while SKILL.md and rules/halo-shapes.md say zones interpolate. Implement it or fix the docs.
box-shadow is painted under a transparent box (user report): in CSS the shadow is clipped to outside the border box.

A test that fails on current main is written first. For anything visual it is a render test (scenario → frame → pixel assertions); tests that build AnimatedProperties by hand are not enough — that is exactly how the regressions listed here slipped through.
Each item is verified end to end: scenario JSON, rustmotion validate, render, image inspected.
cargo fmt --all --check, cargo clippy --workspace --all-targets -- -D warnings, cargo test --workspace pass.
Vocabulary changes update crates/rustmotion/skills/SKILL.md, the relevant rules/ file and the exported schema. A field the validator accepts must have an effect, otherwise the validator rejects it or warns.
No comments in Rust code (repository rule). Commits follow <type>: <verb> <message>. No AI attribution in commits, PRs or issue comments.