Add comprehensive test suite for game mechanics and level handling

- Introduced `test_final_level_flow.py` to validate final level transitions and game end scenarios.
- Created `test_game_over_flow.py` to ensure game over conditions trigger correctly based on rat counts.
- Implemented `test_keybindings.py` to verify keybinding configurations and their context-specific actions.
- Developed `test_level_editor.py` to assess level editor functionalities and layout computations.
- Added `test_level_io.py` for testing level data serialization and deserialization.
- Established `test_loop_logic_parity.py` to ensure consistent game state across multiple simulation runs.
- Created `test_non_regression.py` to simulate game behavior and capture states for future verification.
- Implemented `test_verify.py` to compare current game states against a golden master for regression detection.

units/unit.py

@@ -1,6 +1,16 @@
 from abc import ABC, abstractmethod
 import uuid
+from enum import Enum, auto
 
+class UnitType(Enum):
+    RAT_MALE = auto()
+    RAT_FEMALE = auto()
+    BOMB_TIMER = auto()
+    BOMB_NUCLEAR = auto()
+    GAS = auto()
+    MINE = auto()
+    POINT = auto()
+    EXPLOSION = auto()
 
 class Unit(ABC):
     """
@@ -28,6 +38,8 @@ class Unit(ABC):
         Number of ticks to remain stationary.
     collision_layer : int
         Collision layer for the optimized collision system.
+    type : UnitType
+        The specific type of the unit.
 
     Methods
     -------
@@ -40,7 +52,7 @@ class Unit(ABC):
     die()
         Remove unit from game and handle cleanup.
     """
-    def __init__(self, game, position=(0, 0), id=None, collision_layer=0):
+    def __init__(self, game, position=(0, 0), id=None, collision_layer=0, unit_type=None):
         """Initialize a unit with game reference and position."""
         self.id = id if id else uuid.uuid4()
         self.game = game
@@ -49,9 +61,10 @@ class Unit(ABC):
         self.age = 0
         self.speed = 1.0
         self.partial_move = 0
-        self.bbox = (0, 0, 0, 0)
+        self.bbox = (0.0, 0.0, 0.0, 0.0) # Ensure it's a tuple of floats
         self.stop = 0
         self.collision_layer = collision_layer
+        self.type = unit_type if unit_type else UnitType.POINT # Default type
 
     @abstractmethod
     def move(self):