Convert raw pointers to coordinate-based access (closes #264, closes #265)

GridPoint and GridPointState Python objects now store (grid, x, y)
coordinates instead of raw C++ pointers. Data addresses are computed
on each property access, preventing dangling pointers after vector
resizes.

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

tests/regression/issue_264_gridpoint_dangle_test.py

@@ -0,0 +1,97 @@
+"""Regression test: GridPoint/GridPointState coordinate-based access (#264, #265).
+
+Bug: PyUIGridPointObject stored a raw UIGridPoint* pointer into the grid's
+points vector. PyUIGridPointStateObject stored a raw UIGridPointState*
+into the entity's gridstate vector. If either vector was resized, these
+pointers would dangle.
+
+Fix: Remove raw pointers. Store (grid, x, y) coordinates and compute
+the data address on each property access.
+"""
+import mcrfpy
+import sys
+
+def test_gridpoint_access():
+    """grid.at(x,y) returns working GridPoint via coordinate lookup"""
+    grid = mcrfpy.Grid(grid_size=(10, 10))
+    gp = grid.at(3, 4)
+    assert gp.walkable == False  # default
+    gp.walkable = True
+    assert gp.walkable == True
+    gp.transparent = True
+    assert gp.transparent == True
+    print("  PASS: gridpoint_access")
+
+def test_gridpoint_grid_pos():
+    """GridPoint.grid_pos returns correct coordinates"""
+    grid = mcrfpy.Grid(grid_size=(10, 10))
+    gp = grid.at(7, 3)
+    pos = gp.grid_pos
+    assert pos == (7, 3), f"Expected (7, 3), got {pos}"
+    print("  PASS: gridpoint_grid_pos")
+
+def test_gridpointstate_access():
+    """entity.at(x,y) returns working GridPointState via coordinate lookup"""
+    grid = mcrfpy.Grid(grid_size=(10, 10))
+    entity = mcrfpy.Entity(grid_pos=(5, 5), grid=grid)
+    entity.update_visibility()
+
+    state = entity.at(5, 5)
+    # Should be accessible
+    assert state is not None
+    # visible/discovered should be boolean
+    assert isinstance(state.visible, bool)
+    assert isinstance(state.discovered, bool)
+    print("  PASS: gridpointstate_access")
+
+def test_gridpointstate_after_grid_transfer():
+    """GridPointState access works after entity transfers to new grid"""
+    small = mcrfpy.Grid(grid_size=(10, 10))
+    large = mcrfpy.Grid(grid_size=(20, 20))
+    entity = mcrfpy.Entity(grid_pos=(5, 5), grid=small)
+    entity.update_visibility()
+
+    # Get state on small grid
+    state1 = entity.at(3, 3)
+    assert state1 is not None
+
+    # Transfer to large grid (gridstate resizes)
+    entity.grid = large
+    entity.update_visibility()
+
+    # Access a cell that didn't exist on small grid
+    state2 = entity.at(15, 15)
+    assert state2 is not None
+    print("  PASS: gridpointstate_after_grid_transfer")
+
+def test_gridpoint_subscript():
+    """grid[x, y] returns working GridPoint"""
+    grid = mcrfpy.Grid(grid_size=(10, 10))
+    gp = grid[3, 4]
+    gp.walkable = True
+    assert grid.at(3, 4).walkable == True
+    print("  PASS: gridpoint_subscript")
+
+def test_gridstate_list():
+    """entity.gridstate returns list with visible/discovered attrs"""
+    grid = mcrfpy.Grid(grid_size=(5, 5))
+    entity = mcrfpy.Entity(grid_pos=(2, 2), grid=grid)
+    entity.update_visibility()
+
+    gs = entity.gridstate
+    assert len(gs) == 25, f"Expected 25, got {len(gs)}"
+    # Each element should have visible and discovered
+    for state in gs:
+        assert hasattr(state, 'visible')
+        assert hasattr(state, 'discovered')
+    print("  PASS: gridstate_list")
+
+print("Testing GridPoint/GridPointState coordinate-based access...")
+test_gridpoint_access()
+test_gridpoint_grid_pos()
+test_gridpointstate_access()
+test_gridpointstate_after_grid_transfer()
+test_gridpoint_subscript()
+test_gridstate_list()
+print("PASS: all GridPoint/GridPointState tests passed")
+sys.exit(0)