Three-state spring cursor

One spring position, three swappable heads.

The position is computed once per frame and written to a single wrapper. State is decided by event delegation — mouseover asks the target which cursor it wants, and the heads crossfade in place. Adding a new state costs one element and one selector.

Because everything is driven from one lerped point, the three heads can never desynchronise — a common failure when each element runs its own follow loop.