Rebuild README around the KernelPack numerical stack

Present KernelPack as an end-to-end meshfree toolkit rather than a moving-surface paper artifact. Explain the shared geometry-to-solver architecture, distinguish the sibling implementations, document the complete NumPy/SciPy/Numba capability stack and execution model, balance fixed-domain, moving-domain, manifold, and interpolation workflows, and retain the full publication lineage as research provenance.

Author: VarShankar