feat(tabletop): author rotation and tilt angles in degrees

Convert bgm rotation and tilt values to radians only at the three.js
boundary, so the format's angles are authored in degrees.

packages/tabletop/src/surfaces/WorldSurfaceView.tsx

@@ -10,7 +10,7 @@ import type { Package } from '@tts/bgm';
 import { useRenderState, placementKey } from '../state.js';
 import { PartPlacement } from '../placement.js';
 import type { MountNode } from '../mount.js';
-import { MM_TO_WORLD } from '../part.js';
+import { MM_TO_WORLD, DEG_TO_RAD } from '../part.js';
 import { SurfaceBounds } from './SurfaceBounds.js';
 import { SurfacePlane } from './SurfacePlane.js';
 
@@ -42,7 +42,7 @@ export function SurfaceNode({
   return (
     <group
       position={[node.x * MM_TO_WORLD, 0, node.y * MM_TO_WORLD]}
-      rotation={[0, node.rotation, 0]}
+      rotation={[0, node.rotation * DEG_TO_RAD, 0]}
     >
       {showSurface && (
         <>