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/placement.tsx

@@ -9,7 +9,7 @@ import type { Package } from '@tts/bgm';
 import { useStacking } from './stacking.js';
 import type { Placement } from './state.js';
 import { PartView } from './partView.js';
-import { MM_TO_WORLD } from './part.js';
+import { MM_TO_WORLD, DEG_TO_RAD } from './part.js';
 
 export function PartPlacement({ pkg, placement }: { pkg: Package; placement: Placement }) {
   const { route, candidate, piece, index, stackSize } = placement;
@@ -22,15 +22,16 @@ export function PartPlacement({ pkg, placement }: { pkg: Package; placement: Pla
   // Route anchors and stacking offsets are in mm; convert to world units so
   // parts land on the (world-scaled) surface. `z` raises the part along the
   // surface normal (world +Y); `tilt` fans it about its local Y (long) axis.
+  // Angles are authored in degrees; three.js expects radians.
   const anchorX = ((candidate?.x ?? route.x ?? 0) + x) * MM_TO_WORLD;
   const anchorY = ((candidate?.y ?? route.y ?? 0) + y) * MM_TO_WORLD;
   const anchorZ = z * MM_TO_WORLD;
-  const anchorRotation = (candidate?.rotation ?? route.rotation ?? 0) + rotation;
+  const anchorRotation = ((candidate?.rotation ?? route.rotation ?? 0) + rotation) * DEG_TO_RAD;
 
   return (
     <group position={[anchorX, anchorZ, anchorY]} rotation={[0, anchorRotation, 0]}>
       {/* The part mesh extrudes along +Z; lay it flat so its face points up. */}
-      <group rotation={[-Math.PI / 2, 0, tilt]}>
+      <group rotation={[-Math.PI / 2, 0, tilt * DEG_TO_RAD]}>
         <PartView part={part} baseUrl={part.baseUrl} />
       </group>
     </group>