Task 582: Extract Geometry Helpers from Browser-Only Viewer to Testable Module

Status: DONE

Description

orbital-3d-viewer.js contains geometry helper functions that are untestable

because they depend on Three.js (browser-only). The pure-math logic can be

extracted to orbital-3d-viewer-data.ts and tested in Node.js:

1. arcControlPoint(from, to) → compute Bezier control point at angular midpoint
2. arcControlPointLocal(from, to) → lateral offset for local scenes
3. offsetFromPlanet(point, otherPoint, planetName, sceneType) → displace arc endpoint from planet center

The viewer.js will import these from the data module (via plain [x,y,z] arrays)

and convert to Three.js Vector3 at the call site.

Files

• ts/src/orbital-3d-viewer-data.ts — add exported geometry functions
• ts/src/orbital-3d-viewer-data.test.ts — add tests for geometry functions
• ts/src/orbital-3d-viewer.js — call data module functions instead of local copies