Fix --exec interactive prompt bug and create comprehensive test suite

Major fixes:
- Fixed --exec entering Python REPL instead of game loop
- Resolved screenshot transparency issue (requires timer callbacks)
- Added debug output to trace Python initialization

Test suite created:
- 13 comprehensive tests covering all Python-exposed methods
- Tests use timer callback pattern for proper game loop interaction
- Discovered multiple critical bugs and missing features

Critical bugs found:
- Grid class segfaults on instantiation (blocks all Grid functionality)
- Issue #78 confirmed: Middle mouse click sends 'C' keyboard event
- Entity property setters have argument parsing errors
- Sprite texture setter returns improper error
- keypressScene() segfaults on non-callable arguments

Documentation updates:
- Updated CLAUDE.md with testing guidelines and TDD practices
- Created test reports documenting all findings
- Updated ROADMAP.md with test results and new priorities

The Grid segfault is now the highest priority as it blocks all Grid-based functionality.

tests/screenshot_transparency_fix_test.py

@@ -0,0 +1,77 @@
+#!/usr/bin/env python3
+"""Test and workaround for transparent screenshot issue"""
+import mcrfpy
+from mcrfpy import automation
+from datetime import datetime
+import sys
+
+def test_transparency_workaround():
+    """Create a full-window opaque background to fix transparency"""
+    print("=== Screenshot Transparency Fix Test ===\n")
+    
+    # Create a scene
+    mcrfpy.createScene("opaque_test")
+    mcrfpy.setScene("opaque_test")
+    ui = mcrfpy.sceneUI("opaque_test")
+    
+    # WORKAROUND: Create a full-window opaque frame as the first element
+    # This acts as an opaque background since the scene clears with transparent
+    print("Creating full-window opaque background...")
+    background = mcrfpy.Frame(0, 0, 1024, 768,
+                             fill_color=mcrfpy.Color(50, 50, 50),  # Dark gray
+                             outline_color=None,
+                             outline=0.0)
+    ui.append(background)
+    print("✓ Added opaque background frame")
+    
+    # Now add normal content on top
+    print("\nAdding test content...")
+    
+    # Red frame
+    frame1 = mcrfpy.Frame(100, 100, 200, 150,
+                         fill_color=mcrfpy.Color(255, 0, 0),
+                         outline_color=mcrfpy.Color(255, 255, 255),
+                         outline=3.0)
+    ui.append(frame1)
+    
+    # Green frame
+    frame2 = mcrfpy.Frame(350, 100, 200, 150,
+                         fill_color=mcrfpy.Color(0, 255, 0),
+                         outline_color=mcrfpy.Color(0, 0, 0),
+                         outline=3.0)
+    ui.append(frame2)
+    
+    # Blue frame
+    frame3 = mcrfpy.Frame(100, 300, 200, 150,
+                         fill_color=mcrfpy.Color(0, 0, 255),
+                         outline_color=mcrfpy.Color(255, 255, 0),
+                         outline=3.0)
+    ui.append(frame3)
+    
+    # Add text
+    caption = mcrfpy.Caption(mcrfpy.Vector(250, 50),
+                            text="OPAQUE BACKGROUND TEST",
+                            fill_color=mcrfpy.Color(255, 255, 255))
+    caption.size = 32
+    ui.append(caption)
+    
+    # Take screenshot
+    timestamp = datetime.now().strftime("%Y%m%d_%H%M%S")
+    filename = f"screenshot_opaque_fix_{timestamp}.png"
+    result = automation.screenshot(filename)
+    
+    print(f"\nScreenshot taken: {filename}")
+    print(f"Result: {result}")
+    
+    print("\n=== Analysis ===")
+    print("The issue is that PyScene::render() calls clear() without a color parameter.")
+    print("SFML's default clear color is transparent black (0,0,0,0).")
+    print("In windowed mode, the window provides an opaque background.")
+    print("In headless mode, the RenderTexture preserves the transparency.")
+    print("\nWORKAROUND: Always add a full-window opaque Frame as the first UI element.")
+    print("FIX: Modify PyScene.cpp and UITestScene.cpp to use clear(sf::Color::Black)")
+    
+    sys.exit(0)
+
+# Run immediately
+test_transparency_workaround()