Update "Entity-Management"

Entity-Management.md

@@ -21,7 +21,6 @@ Entities are game objects that implement behavior and live on Grids. While Grids
 **Related Issues:**
 - [#115](../../issues/115) - SpatialHash for fast queries (Open)
 - [#117](../../issues/117) - Memory Pool for entities (Open)
-- [#16](../../issues/16) - Entity knowledge contents (Open)
 
 ---
 
@@ -186,13 +185,69 @@ for state in entity.gridstate:
     print(f"visible={state.visible}, discovered={state.discovered}")
 
 # Access specific cell state
-state = entity.at(x, y)
+state = entity.at((x, y))
 if state.visible:
     print("Entity can currently see this cell")
 elif state.discovered:
     print("Entity has seen this cell before")
 ```
 
+### GridPointState.point - Accessing Cell Data (#16)
+
+The `GridPointState.point` property provides access to the underlying `GridPoint` from an entity's perspective:
+
+```python
+state = entity.at((x, y))
+
+# If entity has NOT discovered this cell, point is None
+if not state.discovered:
+    print(state.point)  # None - entity doesn't know what's here
+
+# If entity HAS discovered the cell, point gives access to GridPoint
+if state.discovered:
+    point = state.point  # Live reference to GridPoint
+    print(f"walkable: {point.walkable}")
+    print(f"transparent: {point.transparent}")
+    print(f"entities here: {point.entities}")  # List of entities at cell
+```
+
+**Key behaviors:**
+- Returns `None` if `discovered=False` (entity has never seen this cell)
+- Returns live `GridPoint` reference if `discovered=True`
+- Changes to the `GridPoint` are immediately visible through `state.point`
+- This is intentionally **not** a cached copy - for historical memory, implement your own system in Python
+
+**Use case - Entity perspective queries:**
+
+```python
+def can_entity_see_walkable_path(entity, x, y):
+    """Check if entity knows this cell is walkable."""
+    state = entity.at((x, y))
+    if state.point is None:
+        return None  # Unknown - entity hasn't discovered it
+    return state.point.walkable
+
+def get_known_entities_at(entity, x, y):
+    """Get entities at cell if entity has discovered it."""
+    state = entity.at((x, y))
+    if state.point is None:
+        return []  # Entity doesn't know this cell
+    return state.point.entities
+```
+
+**Ground truth access:**
+
+If you need the actual cell data regardless of entity perspective, access it through the grid directly:
+
+```python
+# Entity perspective (respects discovered state)
+state = entity.at((x, y))
+point_or_none = state.point
+
+# Ground truth (always returns GridPoint)
+point = entity.grid.at(x, y)
+```
+
 ---
 
 ## EntityCollection
@@ -403,6 +458,12 @@ def entities_at(grid, x, y):
     return [e for e in grid.entities if e.x == x and e.y == y]
 ```
 
+**New in v1.0:** Use `GridPoint.entities` for cell-based queries:
+```python
+# O(n) but more convenient - filters grid.entities by position
+entities_here = grid.at(x, y).entities
+```
+
 **Workarounds:**
 - Keep entity counts reasonable (< 200 for best performance)
 - Use timer callbacks for AI updates, not per-frame