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>

tests/regression/issue_295_cell_pos_test.py

@@ -0,0 +1,78 @@
+"""Regression test for #295: Entity cell_pos integer logical position."""
+import mcrfpy
+import sys
+
+def test_cell_pos_init():
+    """cell_pos initialized from grid_pos on construction."""
+    e = mcrfpy.Entity((5, 7))
+    assert e.cell_x == 5, f"cell_x should be 5, got {e.cell_x}"
+    assert e.cell_y == 7, f"cell_y should be 7, got {e.cell_y}"
+    print("PASS: cell_pos initialized from constructor")
+
+def test_cell_pos_grid_pos_alias():
+    """grid_pos is an alias for cell_pos."""
+    e = mcrfpy.Entity((3, 4))
+    # grid_pos should match cell_pos
+    assert e.grid_pos.x == e.cell_pos.x
+    assert e.grid_pos.y == e.cell_pos.y
+
+    # Setting grid_pos should update cell_pos
+    e.grid_pos = (10, 20)
+    assert e.cell_x == 10
+    assert e.cell_y == 20
+    print("PASS: grid_pos aliases cell_pos")
+
+def test_cell_pos_independent_from_draw_pos():
+    """cell_pos does not change when draw_pos (float position) changes."""
+    e = mcrfpy.Entity((5, 5))
+
+    # Change draw_pos (float position for rendering)
+    e.draw_pos = (5.5, 5.5)
+
+    # cell_pos should be unchanged
+    assert e.cell_x == 5, f"cell_x should still be 5 after draw_pos change, got {e.cell_x}"
+    assert e.cell_y == 5, f"cell_y should still be 5 after draw_pos change, got {e.cell_y}"
+    print("PASS: cell_pos independent from draw_pos")
+
+def test_cell_pos_spatial_hash():
+    """GridPoint.entities uses cell_pos for matching."""
+    scene = mcrfpy.Scene("test295")
+    mcrfpy.current_scene = scene
+    tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    grid = mcrfpy.Grid(grid_size=(20, 20), texture=tex, pos=(0, 0), size=(320, 320))
+    scene.children.append(grid)
+
+    e = mcrfpy.Entity((5, 5), grid=grid)
+
+    # Entity should appear at cell (5, 5)
+    assert len(grid.at(5, 5).entities) == 1
+
+    # Move cell_pos to (10, 10)
+    e.cell_pos = (10, 10)
+    assert len(grid.at(5, 5).entities) == 0, "Old cell should be empty"
+    assert len(grid.at(10, 10).entities) == 1, "New cell should have entity"
+    print("PASS: spatial hash uses cell_pos")
+
+def test_cell_pos_member_access():
+    """cell_x and cell_y read/write correctly."""
+    e = mcrfpy.Entity((3, 7))
+    assert e.cell_x == 3
+    assert e.cell_y == 7
+
+    e.cell_x = 15
+    assert e.cell_x == 15
+    assert e.cell_y == 7  # y unchanged
+
+    e.cell_y = 20
+    assert e.cell_x == 15  # x unchanged
+    assert e.cell_y == 20
+    print("PASS: cell_x/cell_y member access")
+
+if __name__ == "__main__":
+    test_cell_pos_init()
+    test_cell_pos_grid_pos_alias()
+    test_cell_pos_independent_from_draw_pos()
+    test_cell_pos_spatial_hash()
+    test_cell_pos_member_access()
+    print("All #295 tests passed")
+    sys.exit(0)