Fullwave example

[djps]

Fixes #649.

Summary by CodeRabbit

• Documentation

  • Added a new "Simple Plane Wave" example with README and Colab integration.

• New Features

  • Added utilities to map mask data to coordinates and to generate Gaussian‑modulated pulse signals.
  • Included a complete 2D full‑wave simulation workflow with multi‑layer source support, sensor capture, visualization, animation, and export.

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