Implement the foundational HeightMap class for procedural generation:
- HeightMap(size, fill=0.0) constructor with libtcod backend
- Immutable size property after construction
- Scalar operations returning self for method chaining:
- fill(value), clear()
- add_constant(value), scale(factor)
- clamp(min=0.0, max=1.0), normalize(min=0.0, max=1.0)
Includes procedural generation spec document and unit tests.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
