Phase 2: Entity data model extensions for behavior system

- Add Behavior enum (IDLE..FLEE, 11 values) and Trigger enum (DONE,
  BLOCKED, TARGET) as runtime IntEnum classes (closes #297, closes #298)
- Add entity label system: labels property (frozenset), add_label(),
  remove_label(), has_label(), constructor kwarg (closes #296)
- Add cell_pos integer logical position decoupled from float draw_pos;
  grid_pos now aliases cell_pos; SpatialHash::updateCell() for cell-based
  bucket management; FOV/visibility uses cell_position (closes #295)
- Add step callback and default_behavior properties to Entity for
  grid.step() turn management (closes #299)
- Update updateVisibility, visible_entities, ColorLayer::updatePerspective
  to use cell_position instead of float position

BREAKING: grid_pos no longer derives from float x/y position. Use
cell_pos/grid_pos for logical position, draw_pos for render position.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/PyTrigger.h

@@ -0,0 +1,21 @@
+#pragma once
+#include "Common.h"
+#include "Python.h"
+
+// Module-level Trigger enum class (created at runtime using Python's IntEnum)
+// Stored as a module attribute: mcrfpy.Trigger
+//
+// Values represent trigger types passed to entity step() callbacks.
+
+class PyTrigger {
+public:
+    // Create the Trigger enum class and add to module
+    // Returns the enum class (new reference), or NULL on error
+    static PyObject* create_enum_class(PyObject* module);
+
+    // Cached reference to the Trigger enum class for fast type checking
+    static PyObject* trigger_enum_class;
+
+    // Number of trigger types
+    static const int NUM_TRIGGERS = 3;
+};