Add Pygame and Arcade mocking support for educational game development

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This PR implements comprehensive mocking support for both Pygame and Arcade, the two most popular Python game development libraries used in educational settings.

What's Added

Arcade Mock (MockArcade)

Arcade is a modern, Pythonic game library designed specifically for education. The mock captures:

• Window management (open_window, set_background_color, close_window)
• Drawing operations (circles, rectangles, lines, text)
• Sprite creation and management with physics
• Sound loading and playback
• Game loop scheduling and timing
• Collision detection functions
• Color constants

Pygame Mock (MockPygame)

Pygame is the classic Python game library with widespread adoption. The mock captures:

• Core initialization and cleanup (pygame.init(), pygame.quit())
• Display management (pygame.display.set_mode(), pygame.display.flip())
• Drawing functions (pygame.draw.rect(), pygame.draw.circle(), etc.)
• Event handling (pygame.event.get())
• Sound/mixer support (pygame.mixer.Sound)
• Clock and timing (pygame.time.Clock)
• Surface, Color, and Rect object creation

Educational Benefits

Both mocks follow the same pattern as the existing matplotlib mock, allowing educators to:

• Inspect student game development code without requiring actual game libraries
• Verify that students are using proper game development patterns
• Track drawing operations, sprite interactions, and game state
• Provide automated feedback on game structure and logic

Example Usage

# Student code that would normally require Arcade installation
import arcade

arcade.open_window(800, 600, "My Game")
arcade.set_background_color(arcade.color.WHITE)

arcade.start_render()
arcade.draw_circle_filled(100, 100, 50, arcade.color.RED)
arcade.finish_render()

# Educator can now inspect the mock data
sandbox = get_sandbox()
arcade_mock = sandbox.modules.arcade
assert len(arcade_mock.draw_commands) == 3  # start_render, circle, finish_render
assert arcade_mock.window['title'] == "My Game"

The implementation includes comprehensive test coverage with both unit tests for the mock classes and integration tests demonstrating usage within the pedal sandbox system.

Fixes #9.

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