Fix mypy error: remove narrowing ClassVar[Literal] annotations from layout subclasses

Horizontal extends Vertical, and Fat extends Tall. Declaring
drag_overlay_mode with a narrower Literal type in the subclass
conflicts with the parent's declared type, causing mypy error
"Incompatible types in assignment". Since the base Layout class already
declares the full union type, subclasses only need a bare assignment.

Also removes now-unused ClassVar and Literal imports from vertical.py,
tall.py, and grid.py.

kitty/layout/grid.py

@@ -5,7 +5,7 @@ from collections.abc import Callable, Generator, Iterator, Sequence
 from functools import lru_cache
 from itertools import repeat
 from math import ceil, floor
-from typing import Any, ClassVar, Literal
+from typing import Any
 
 from kitty.borders import BorderColor
 from kitty.types import Edges, NeighborsMap, WindowMapper
@@ -34,7 +34,7 @@ class Grid(Layout):
 
     name: str = 'grid'
     no_minimal_window_borders = True
-    drag_overlay_mode: ClassVar[Literal['axis_y']] = 'axis_y'
+    drag_overlay_mode = 'axis_y'
 
     def remove_all_biases(self) -> bool:
         self.biased_rows: dict[int, float] = {}

kitty/layout/splits.py

@@ -561,7 +561,7 @@ class Splits(Layout):
     needs_all_windows = True
     layout_opts = SplitsLayoutOpts({})
     no_minimal_window_borders = True
-    drag_overlay_mode: ClassVar[Literal['free']] = 'free'
+    drag_overlay_mode = 'free'
 
     @property
     def default_axis_is_horizontal(self) -> bool | None:

kitty/layout/tall.py

@@ -4,7 +4,7 @@
 import sys
 from collections.abc import Generator, Iterator, Sequence
 from itertools import islice, repeat
-from typing import Any, ClassVar, Literal
+from typing import Any
 
 from kitty.borders import BorderColor
 from kitty.conf.utils import to_bool
@@ -136,7 +136,7 @@ class Tall(Layout):
     name = 'tall'
     main_is_horizontal = True
     no_minimal_window_borders = True
-    drag_overlay_mode: ClassVar[Literal['axis_y']] = 'axis_y'
+    drag_overlay_mode = 'axis_y'
     layout_opts = TallLayoutOpts({})
     main_axis_layout = Layout.xlayout
     perp_axis_layout = Layout.ylayout
@@ -382,6 +382,6 @@ class Fat(Tall):
 
     name = 'fat'
     main_is_horizontal = False
-    drag_overlay_mode: ClassVar[Literal['axis_x']] = 'axis_x'
+    drag_overlay_mode = 'axis_x'
     main_axis_layout = Layout.ylayout
     perp_axis_layout = Layout.xlayout

kitty/layout/vertical.py

@@ -2,7 +2,7 @@
 # License: GPLv3 Copyright: 2020, Kovid Goyal <kovid at kovidgoyal.net>
 
 from collections.abc import Generator, Iterable
-from typing import Any, ClassVar, Literal
+from typing import Any
 
 from kitty.borders import BorderColor
 from kitty.types import Edges, NeighborsMap, WindowMapper
@@ -64,7 +64,7 @@ class Vertical(Layout):
     name = 'vertical'
     main_is_horizontal = False
     no_minimal_window_borders = True
-    drag_overlay_mode: ClassVar[Literal['axis_y']] = 'axis_y'
+    drag_overlay_mode = 'axis_y'
     main_axis_layout = Layout.ylayout
     perp_axis_layout = Layout.xlayout
 
@@ -156,6 +156,6 @@ class Horizontal(Vertical):
 
     name = 'horizontal'
     main_is_horizontal = True
-    drag_overlay_mode: ClassVar[Literal['axis_x']] = 'axis_x'
+    drag_overlay_mode = 'axis_x'
     main_axis_layout = Layout.xlayout
     perp_axis_layout = Layout.ylayout