Fix gridstate heap overflows and spatial hash cleanup

Add ensureGridstate() helper that unconditionally checks gridstate size
against current grid dimensions and resizes if mismatched. Replace all
lazy-init guards (size == 0) with ensureGridstate() calls.

Previously, gridstate was only initialized when empty. When an entity
moved to a differently-sized grid, gridstate kept the old size, causing
heap buffer overflows when updateVisibility() or at() iterated using the
new grid's dimensions.

Also adds spatial_hash.remove() calls in set_grid() before removing
entities from old grids, and replaces PyObject_GetAttrString type lookup
with direct &mcrfpydef::PyUIGridType reference.

Closes #258, closes #259, closes #260, closes #261, closes #262,
closes #263, closes #274, closes #276, closes #278

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/regression/issue_258_gridstate_resize_test.py

@@ -0,0 +1,175 @@
+"""Regression test: entity gridstate must resize when moving between grids.
+
+Issues #258-#263, #274, #276, #278: UIEntity gridstate heap overflows.
+
+Bug: Gridstate was only initialized when empty (size == 0). When an entity
+moved from a small grid to a larger grid via ANY transfer method, gridstate
+kept the old size. Code then iterated using the new grid's dimensions,
+writing past the vector's end.
+
+Fix: ensureGridstate() unconditionally checks gridstate.size() against
+grid dimensions and resizes if they don't match. Applied to all transfer
+methods: set_grid, append, extend, insert, setitem, slice assignment.
+
+Also tests #274: spatial_hash.remove() must be called when removing
+entities from grids via set_grid(None) or set_grid(other_grid).
+"""
+import mcrfpy
+import sys
+
+def test_set_grid():
+    """entity.grid = new_grid resizes gridstate"""
+    small = mcrfpy.Grid(grid_size=(10, 10))
+    large = mcrfpy.Grid(grid_size=(50, 50))
+    entity = mcrfpy.Entity(grid_pos=(5, 5), grid=small)
+
+    small.perspective = entity
+    small.fov_radius = 4
+    entity.update_visibility()
+
+    gs = entity.gridstate
+    assert len(gs) == 100, f"Expected 100, got {len(gs)}"
+
+    entity.grid = large
+    gs = entity.gridstate
+    assert len(gs) == 2500, f"Expected 2500, got {len(gs)}"
+
+    large.perspective = entity
+    large.fov_radius = 8
+    entity.update_visibility()
+    print("  PASS: set_grid")
+
+def test_append():
+    """grid.entities.append(entity) resizes gridstate"""
+    small = mcrfpy.Grid(grid_size=(10, 10))
+    large = mcrfpy.Grid(grid_size=(40, 40))
+    entity = mcrfpy.Entity(grid_pos=(3, 3), grid=small)
+    entity.update_visibility()
+
+    gs = entity.gridstate
+    assert len(gs) == 100, f"Expected 100, got {len(gs)}"
+
+    large.entities.append(entity)
+    gs = entity.gridstate
+    assert len(gs) == 1600, f"Expected 1600, got {len(gs)}"
+    print("  PASS: append")
+
+def test_extend():
+    """grid.entities.extend([entity]) resizes gridstate"""
+    small = mcrfpy.Grid(grid_size=(10, 10))
+    large = mcrfpy.Grid(grid_size=(30, 30))
+    entity = mcrfpy.Entity(grid_pos=(3, 3), grid=small)
+    entity.update_visibility()
+
+    large.entities.extend([entity])
+    gs = entity.gridstate
+    assert len(gs) == 900, f"Expected 900, got {len(gs)}"
+    print("  PASS: extend")
+
+def test_insert():
+    """grid.entities.insert(0, entity) resizes gridstate"""
+    small = mcrfpy.Grid(grid_size=(10, 10))
+    large = mcrfpy.Grid(grid_size=(25, 25))
+    entity = mcrfpy.Entity(grid_pos=(3, 3), grid=small)
+    entity.update_visibility()
+
+    large.entities.insert(0, entity)
+    gs = entity.gridstate
+    assert len(gs) == 625, f"Expected 625, got {len(gs)}"
+    print("  PASS: insert")
+
+def test_setitem():
+    """grid.entities[0] = entity resizes gridstate"""
+    small = mcrfpy.Grid(grid_size=(10, 10))
+    large = mcrfpy.Grid(grid_size=(20, 20))
+    entity = mcrfpy.Entity(grid_pos=(3, 3), grid=small)
+    entity.update_visibility()
+
+    # Need a placeholder entity in large grid first
+    placeholder = mcrfpy.Entity(grid_pos=(0, 0), grid=large)
+    large.entities[0] = entity
+    gs = entity.gridstate
+    assert len(gs) == 400, f"Expected 400, got {len(gs)}"
+    print("  PASS: setitem")
+
+def test_slice_assign():
+    """grid.entities[0:1] = [entity] resizes gridstate"""
+    small = mcrfpy.Grid(grid_size=(10, 10))
+    large = mcrfpy.Grid(grid_size=(35, 35))
+    entity = mcrfpy.Entity(grid_pos=(3, 3), grid=small)
+    entity.update_visibility()
+
+    placeholder = mcrfpy.Entity(grid_pos=(0, 0), grid=large)
+    large.entities[0:1] = [entity]
+    gs = entity.gridstate
+    assert len(gs) == 1225, f"Expected 1225, got {len(gs)}"
+    print("  PASS: slice_assign")
+
+def test_update_visibility_after_transfer():
+    """update_visibility works correctly after all transfer methods"""
+    grids = [mcrfpy.Grid(grid_size=(s, s)) for s in (5, 80, 3, 60, 10, 100)]
+    entity = mcrfpy.Entity(grid_pos=(2, 2), grid=grids[0])
+
+    for g in grids:
+        entity.grid = g
+        g.perspective = entity
+        g.fov_radius = 4
+        entity.update_visibility()
+        gs = entity.gridstate
+        expected = g.grid_w * g.grid_h
+        assert len(gs) == expected, f"Expected {expected}, got {len(gs)}"
+    print("  PASS: update_visibility_after_transfer")
+
+def test_at_after_transfer():
+    """entity.at(x, y) works correctly after grid transfer"""
+    small = mcrfpy.Grid(grid_size=(10, 10))
+    large = mcrfpy.Grid(grid_size=(50, 50))
+    entity = mcrfpy.Entity(grid_pos=(5, 5), grid=small)
+    entity.update_visibility()
+
+    entity.grid = large
+    # Access a cell that would be out of bounds for the small grid
+    state = entity.at(30, 30)
+    assert state is not None
+    print("  PASS: at_after_transfer")
+
+def test_set_grid_none():
+    """entity.grid = None properly removes entity (tests #274)"""
+    grid = mcrfpy.Grid(grid_size=(10, 10))
+    entity = mcrfpy.Entity(grid_pos=(5, 5), grid=grid)
+    assert len(grid.entities) == 1
+    entity.grid = None
+    assert len(grid.entities) == 0
+    print("  PASS: set_grid_none")
+
+def test_stress():
+    """Stress test: rapid grid transfers with heap churn"""
+    entity = mcrfpy.Entity(grid_pos=(2, 2))
+    for i in range(20):
+        small_g = mcrfpy.Grid(grid_size=(5, 5))
+        entity.grid = small_g
+        small_g.perspective = entity
+        entity.update_visibility()
+
+        big_g = mcrfpy.Grid(grid_size=(80, 80))
+        entity.grid = big_g
+        big_g.perspective = entity
+        entity.update_visibility()
+
+        frames = [mcrfpy.Frame() for _ in range(10)]
+        del frames
+    print("  PASS: stress")
+
+print("Testing gridstate resize across transfer methods...")
+test_set_grid()
+test_append()
+test_extend()
+test_insert()
+test_setitem()
+test_slice_assign()
+test_update_visibility_after_transfer()
+test_at_after_transfer()
+test_set_grid_none()
+test_stress()
+print("PASS: all gridstate resize tests passed")
+sys.exit(0)