Mesh: remove post-stop settling motion

Details

Drop the per-vertex spring (velocity/damping) and drive each vertex
directly from the current cursor position. The grid now warps only while
the cursor is moving and is completely static the instant it stops — no
residual settling or wobble. A gentle fade still flattens the dimple
when the cursor leaves the page, and the rAF loop idles when nothing is
moving.

Files changed (1)