Fix verify-pass code bugs #317/#318/#319

Three small bugs surfaced by the #314 docstring-accuracy verify pass:

#317 automation.scroll() dropped the x of its position argument: scroll()
resolved (x, y) but called injectMouseEvent(MouseWheelScrolled, clicks, y),
passing the scroll amount as x. injectMouseEvent now takes the scroll delta as
its own parameter and scroll() forwards the real x/y.

#318 GridView.texture always returned None (a TODO stub). It now returns a
Texture wrapper sharing the underlying shared_ptr<PyTexture>, mirroring
Grid.texture. (mcrfpy.Grid and mcrfpy.GridView are the same type post-#252, so
this fixes both names.)

#319 Entity.visible_entities(radius=None) raised TypeError: radius was parsed
with the 'i' format code, which rejects None. It now parses radius as an object
and treats None / omitted / -1 as "use the grid's default fov_radius"; a
non-int, non-None radius raises a clear TypeError.

- regression tests for each under tests/regression/
- api_surface snapshot re-baselined (visible_entities signature; texture
  property now Texture | None) and docs/stubs regenerated; frozen docstring
  gate still 100%

closes #317
closes #318
closes #319

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KnywUddaFRhkxo5kijxJnv

stubs/mcrfpy.pyi

@@ -725,7 +725,7 @@ class Entity:
     def update_visibility(self) -> None:
         """Recompute which cells are visible from this entity's position and update perspective_map."""
         ...
-    def visible_entities(self, fov=None, radius: int = -1) -> list[Entity]:
+    def visible_entities(self, fov=None, radius: int | None = None) -> list[Entity]:
         """Get list of other entities visible from this entity's position."""
         ...
 
@@ -903,7 +903,7 @@ class Grid:
     rotation: Any  # Rotation angle in degrees (clockwise around origin). Animatable property.
     shader: Any  # Shader for GPU visual effects (Shader or None). When set, the drawable is rendered through the shader program. Set to None to disable shader effects.
     size: Vector  # Size of the grid widget as Vector (Vector, width x height in pixels).
-    texture: None  # Texture used for tile rendering (None, read-only). Texture return is not yet implemented; always returns None.
+    texture: Texture | None  # Texture used for tile rendering (Texture | None, read-only).
     uniforms: Any  # Collection of shader uniforms (read-only access to collection). Set uniforms via dict-like syntax: drawable.uniforms['name'] = value. Supports float, vec2/3/...
     vert_margin: float  # Vertical margin override (float, 0 = use general margin). Invalid for horizontally-centered alignments (CENTER_LEFT, CENTER_RIGHT, CENTER).
     view: GridView | None  # Auto-created GridView for rendering (GridView | None, read-only). When Grid is appended to a scene, this view is what actually renders.
@@ -1013,7 +1013,7 @@ class GridView:
     rotation: Any  # Rotation angle in degrees (clockwise around origin). Animatable property.
     shader: Any  # Shader for GPU visual effects (Shader or None). When set, the drawable is rendered through the shader program. Set to None to disable shader effects.
     size: Vector  # Size of the grid widget as Vector (Vector, width x height in pixels).
-    texture: None  # Texture used for tile rendering (None, read-only). Texture return is not yet implemented; always returns None.
+    texture: Texture | None  # Texture used for tile rendering (Texture | None, read-only).
     uniforms: Any  # Collection of shader uniforms (read-only access to collection). Set uniforms via dict-like syntax: drawable.uniforms['name'] = value. Supports float, vec2/3/...
     vert_margin: float  # Vertical margin override (float, 0 = use general margin). Invalid for horizontally-centered alignments (CENTER_LEFT, CENTER_RIGHT, CENTER).
     view: GridView | None  # Auto-created GridView for rendering (GridView | None, read-only). When Grid is appended to a scene, this view is what actually renders.