Vectors and Motion Bridge is still in progress

Start with vectors as geometric objects on a 2D plane, then carry the same component language into the existing motion-facing vectors bench.

This completion page stays public, but the completion reflection only unlocks after every concept and authored checkpoint in this track is clear on this browser. The route still reads the same local concept records and solved challenge ids, and signed-in sync keeps reusing those records instead of inventing a separate track store.