HeightMap: core class with scalar operations (closes #193)

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>

src/PyHeightMap.h

@@ -0,0 +1,67 @@
+#pragma once
+#include "Common.h"
+#include "Python.h"
+#include <libtcod.h>
+
+// Forward declaration
+class PyHeightMap;
+
+// Python object structure
+typedef struct {
+    PyObject_HEAD
+    TCOD_heightmap_t* heightmap;  // libtcod heightmap pointer
+} PyHeightMapObject;
+
+class PyHeightMap
+{
+public:
+    // Python type interface
+    static PyObject* pynew(PyTypeObject* type, PyObject* args, PyObject* kwds);
+    static int init(PyHeightMapObject* self, PyObject* args, PyObject* kwds);
+    static void dealloc(PyHeightMapObject* self);
+    static PyObject* repr(PyObject* obj);
+
+    // Properties
+    static PyObject* get_size(PyHeightMapObject* self, void* closure);
+
+    // Scalar operations (all return self for chaining)
+    static PyObject* fill(PyHeightMapObject* self, PyObject* args);
+    static PyObject* clear(PyHeightMapObject* self, PyObject* Py_UNUSED(args));
+    static PyObject* add_constant(PyHeightMapObject* self, PyObject* args);
+    static PyObject* scale(PyHeightMapObject* self, PyObject* args);
+    static PyObject* clamp(PyHeightMapObject* self, PyObject* args, PyObject* kwds);
+    static PyObject* normalize(PyHeightMapObject* self, PyObject* args, PyObject* kwds);
+
+    // Method and property definitions
+    static PyMethodDef methods[];
+    static PyGetSetDef getsetters[];
+};
+
+namespace mcrfpydef {
+    static PyTypeObject PyHeightMapType = {
+        .ob_base = {.ob_base = {.ob_refcnt = 1, .ob_type = NULL}, .ob_size = 0},
+        .tp_name = "mcrfpy.HeightMap",
+        .tp_basicsize = sizeof(PyHeightMapObject),
+        .tp_itemsize = 0,
+        .tp_dealloc = (destructor)PyHeightMap::dealloc,
+        .tp_repr = PyHeightMap::repr,
+        .tp_flags = Py_TPFLAGS_DEFAULT,
+        .tp_doc = PyDoc_STR(
+            "HeightMap(size: tuple[int, int], fill: float = 0.0)\n\n"
+            "A 2D grid of float values for procedural generation.\n\n"
+            "HeightMap is the universal canvas for procedural generation. It stores "
+            "float values that can be manipulated, combined, and applied to Grid and "
+            "Layer objects.\n\n"
+            "Args:\n"
+            "    size: (width, height) dimensions of the heightmap. Immutable after creation.\n"
+            "    fill: Initial value for all cells. Default 0.0.\n\n"
+            "Example:\n"
+            "    hmap = mcrfpy.HeightMap((100, 100))\n"
+            "    hmap.fill(0.5).scale(2.0).clamp(0.0, 1.0)\n"
+        ),
+        .tp_methods = nullptr,  // Set in McRFPy_API.cpp before PyType_Ready
+        .tp_getset = nullptr,   // Set in McRFPy_API.cpp before PyType_Ready
+        .tp_init = (initproc)PyHeightMap::init,
+        .tp_new = PyHeightMap::pynew,
+    };
+}