Resolves #7839

Before

beginShape(POINTS) ignored per‑vertex stroke() changes because the point shader used a uniform uMaterialColor only; lines/triangles already passed aVertexColor and interpolated as expected. This made POINTS single‑color even when stroke() was set per vertex.

After

POINTS now honor per‑vertex stroke colors by passing aVertexColor to the point shader and binding it from vertexStrokeColors. Single point() continues to use the uniform stroke color.

Behavior

beginShape(POINTS) now renders each vertex with its own stroke() color.
point() (standalone) continues to use the uniform stroke() color.
LINES/TRIANGLES behavior unchanged.