Fix GridView.grid property and add sanitizer stress test

- Implement GridView.grid getter: reconstruct shared_ptr<UIGrid> from
  aliasing grid_data pointer, use PythonObjectCache for identity
  preservation (view.grid is grid == True)
- Add sanitizer stress test exercising entity lifecycle, behavior
  stepping, GridView lifecycle, FOV dedup, and spatial hash churn
- Add GridView.grid identity test

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

tests/integration/sanitizer_stress_test.py

@@ -0,0 +1,173 @@
+"""Stress test for sanitizer builds: exercises new Phase 1-4 code paths."""
+import mcrfpy
+import sys
+
+def stress_entity_lifecycle():
+    """Create/destroy many entities, exercise spatial hash and labels."""
+    scene = mcrfpy.Scene("stress_lifecycle")
+    mcrfpy.current_scene = scene
+    tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    grid = mcrfpy.Grid(grid_size=(50, 50), texture=tex, pos=(0, 0), size=(400, 400))
+    scene.children.append(grid)
+
+    for y in range(50):
+        for x in range(50):
+            grid.at(x, y).walkable = True
+            grid.at(x, y).transparent = True
+
+    # Create many entities
+    entities = []
+    for i in range(100):
+        e = mcrfpy.Entity((i % 48 + 1, i // 48 + 1), grid=grid,
+                          labels={"test", f"group_{i % 5}"})
+        e.cell_pos = (i % 48 + 1, i // 48 + 1)
+        entities.append(e)
+
+    # Verify spatial hash
+    cell_ents = grid.at(1, 1).entities
+    assert len(cell_ents) >= 1, f"Expected entities at (1,1), got {len(cell_ents)}"
+
+    # Move entities around
+    for i, e in enumerate(entities):
+        new_x = (i * 7 + 3) % 48 + 1
+        new_y = (i * 13 + 5) % 48 + 1
+        e.cell_pos = (new_x, new_y)
+
+    # Remove half via die()
+    for e in entities[:50]:
+        e.die()
+
+    # Verify remaining
+    assert len(grid.entities) == 50
+    print("PASS: entity lifecycle stress")
+
+def stress_behavior_stepping():
+    """Run many steps with various behaviors."""
+    scene = mcrfpy.Scene("stress_behavior")
+    mcrfpy.current_scene = scene
+    tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    grid = mcrfpy.Grid(grid_size=(30, 30), texture=tex, pos=(0, 0), size=(300, 300))
+    scene.children.append(grid)
+
+    for y in range(30):
+        for x in range(30):
+            grid.at(x, y).walkable = True
+            grid.at(x, y).transparent = True
+    # Walls on border
+    for i in range(30):
+        grid.at(0, i).walkable = False
+        grid.at(29, i).walkable = False
+        grid.at(i, 0).walkable = False
+        grid.at(i, 29).walkable = False
+
+    # Noise entities
+    for i in range(20):
+        e = mcrfpy.Entity((5 + i, 10), grid=grid)
+        e.set_behavior(int(mcrfpy.Behavior.NOISE4))
+        e.move_speed = 0
+
+    # Sleep entity with callback
+    triggered = []
+    sleeper = mcrfpy.Entity((15, 15), grid=grid)
+    sleeper.set_behavior(int(mcrfpy.Behavior.SLEEP), turns=3)
+    sleeper.step = lambda t, d: triggered.append(int(t))
+
+    # Run 10 steps
+    grid.step(n=10)
+
+    assert len(triggered) == 1, f"Expected 1 DONE trigger, got {len(triggered)}"
+    assert triggered[0] == int(mcrfpy.Trigger.DONE)
+    print("PASS: behavior stepping stress")
+
+def stress_gridview_lifecycle():
+    """Create and destroy multiple GridViews referencing same grid."""
+    scene = mcrfpy.Scene("stress_gridview")
+    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=(200, 200))
+    scene.children.append(grid)
+
+    # Create and destroy views repeatedly
+    for i in range(20):
+        view = mcrfpy.GridView(grid=grid, pos=(220, i * 10), size=(100, 100), zoom=0.5 + i * 0.1)
+        scene.children.append(view)
+
+    # Scene should have grid + 20 views
+    assert len(scene.children) == 21
+
+    # Clear scene children (destroys all views)
+    # Use a new scene instead (children released when scene is replaced)
+    scene2 = mcrfpy.Scene("stress_gridview2")
+    mcrfpy.current_scene = scene2
+
+    # Grid should still be valid
+    assert grid.grid_w == 20
+    print("PASS: GridView lifecycle stress")
+
+def stress_fov_dedup():
+    """Hammer FOV computation with same and different params."""
+    scene = mcrfpy.Scene("stress_fov")
+    mcrfpy.current_scene = scene
+    tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    grid = mcrfpy.Grid(grid_size=(50, 50), texture=tex, pos=(0, 0), size=(400, 400))
+    scene.children.append(grid)
+
+    for y in range(50):
+        for x in range(50):
+            grid.at(x, y).walkable = True
+            grid.at(x, y).transparent = True
+
+    # Same params - should hit dedup cache
+    for _ in range(100):
+        grid.compute_fov((25, 25), radius=10)
+
+    # Different params each time
+    for i in range(50):
+        grid.compute_fov((i, 25), radius=5)
+
+    # Change map then recompute (dirty flag)
+    grid.at(20, 25).transparent = False
+    grid.compute_fov((25, 25), radius=10)
+    assert not grid.is_in_fov((15, 25))  # Blocked by wall
+    print("PASS: FOV dedup stress")
+
+def stress_cell_pos_spatial_hash():
+    """Churn entity positions, verify spatial hash integrity."""
+    scene = mcrfpy.Scene("stress_spatial")
+    mcrfpy.current_scene = scene
+    tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+    grid = mcrfpy.Grid(grid_size=(100, 100), texture=tex, pos=(0, 0), size=(400, 400))
+    scene.children.append(grid)
+
+    for y in range(100):
+        for x in range(100):
+            grid.at(x, y).walkable = True
+
+    # Create entities
+    ents = []
+    for i in range(50):
+        e = mcrfpy.Entity((i + 1, 1), grid=grid)
+        ents.append(e)
+
+    # Move them all to the same cell
+    for e in ents:
+        e.cell_pos = (50, 50)
+
+    assert len(grid.at(50, 50).entities) == 50
+
+    # Scatter them
+    for i, e in enumerate(ents):
+        e.cell_pos = (i + 1, 50)
+
+    assert len(grid.at(50, 50).entities) == 1  # Only entity at index 49
+    assert len(grid.at(1, 50).entities) == 1
+    print("PASS: spatial hash churn stress")
+
+if __name__ == "__main__":
+    stress_entity_lifecycle()
+    stress_behavior_stepping()
+    stress_gridview_lifecycle()
+    stress_fov_dedup()
+    stress_cell_pos_spatial_hash()
+    print("All sanitizer stress tests passed")
+    sys.exit(0)