Fix documentation

Attempt to make sentinel workarounds look as nice as possible

Author: HexDecimal

docs/api.rst

@@ -5,7 +5,7 @@ API reference
    :members:
    :undoc-members:
    :show-inheritance:
-   :exclude-members: Registry, World, Entity
+   :exclude-members: Registry, World, Entity, IsA
 
 .. automodule:: tcod.ecs.registry
    :members:

tcod/ecs/constants.py

@@ -2,6 +2,8 @@
 
 from __future__ import annotations
 
+from typing_extensions import Never
+
 
 class _IgnoreSetState(type):
     def __setstate__(cls, _state: object) -> None:
@@ -11,9 +13,8 @@ def __setstate__(cls, _state: object) -> None:
 class IsA(metaclass=_IgnoreSetState):
     """The default is-a relationship tag used for entity inheritance."""
 
-    def __new__(cls: type[IsA], *_args: object) -> type[IsA]:  # type: ignore[misc]
-        """Return own type instead of instance, for outdated sentinel-value pickle data."""
-        return cls
+    def __new__(cls: type[IsA], *_: object) -> Never:  # noqa: D102
+        return cls  # Return own type instead of instance, for outdated sentinel-value pickle data.
 
 
 _sentinel_IsA = IsA  # Compatibility with sentinel-value, deprecated since 5.4  # noqa: N816