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/validate_screenshot_test.py

@@ -0,0 +1,116 @@
+#!/usr/bin/env python3
+"""Validate screenshot functionality and analyze pixel data"""
+import mcrfpy
+from mcrfpy import automation
+from datetime import datetime
+import sys
+
+def test_screenshot_validation():
+    """Create visible content and validate screenshot output"""
+    print("=== Screenshot Validation Test ===\n")
+    
+    # Create a scene with bright, visible content
+    mcrfpy.createScene("screenshot_validation")
+    mcrfpy.setScene("screenshot_validation")
+    ui = mcrfpy.sceneUI("screenshot_validation")
+    
+    # Create multiple colorful elements to ensure visibility
+    print("Creating UI elements...")
+    
+    # Bright red frame with white outline
+    frame1 = mcrfpy.Frame(50, 50, 300, 200,
+                         fill_color=mcrfpy.Color(255, 0, 0),      # Bright red
+                         outline_color=mcrfpy.Color(255, 255, 255), # White
+                         outline=5.0)
+    ui.append(frame1)
+    print("Added red frame at (50, 50)")
+    
+    # Bright green frame
+    frame2 = mcrfpy.Frame(400, 50, 300, 200,
+                         fill_color=mcrfpy.Color(0, 255, 0),      # Bright green
+                         outline_color=mcrfpy.Color(0, 0, 0),     # Black
+                         outline=3.0)
+    ui.append(frame2)
+    print("Added green frame at (400, 50)")
+    
+    # Blue frame
+    frame3 = mcrfpy.Frame(50, 300, 300, 200,
+                         fill_color=mcrfpy.Color(0, 0, 255),      # Bright blue
+                         outline_color=mcrfpy.Color(255, 255, 0), # Yellow
+                         outline=4.0)
+    ui.append(frame3)
+    print("Added blue frame at (50, 300)")
+    
+    # Add text captions
+    caption1 = mcrfpy.Caption(mcrfpy.Vector(60, 60),
+                             text="RED FRAME TEST",
+                             fill_color=mcrfpy.Color(255, 255, 255))
+    caption1.size = 24
+    frame1.children.append(caption1)
+    
+    caption2 = mcrfpy.Caption(mcrfpy.Vector(410, 60),
+                             text="GREEN FRAME TEST",
+                             fill_color=mcrfpy.Color(0, 0, 0))
+    caption2.size = 24
+    ui.append(caption2)
+    
+    caption3 = mcrfpy.Caption(mcrfpy.Vector(60, 310),
+                             text="BLUE FRAME TEST",
+                             fill_color=mcrfpy.Color(255, 255, 0))
+    caption3.size = 24
+    ui.append(caption3)
+    
+    # White background frame to ensure non-transparent background
+    background = mcrfpy.Frame(0, 0, 1024, 768,
+                             fill_color=mcrfpy.Color(200, 200, 200))  # Light gray
+    # Insert at beginning so it's behind everything
+    ui.remove(len(ui) - 1)  # Remove to re-add at start
+    ui.append(background)
+    # Re-add all other elements on top
+    for frame in [frame1, frame2, frame3, caption2, caption3]:
+        ui.append(frame)
+    
+    print(f"\nTotal UI elements: {len(ui)}")
+    
+    # Take multiple screenshots with different names
+    timestamp = datetime.now().strftime("%Y%m%d_%H%M%S")
+    
+    screenshots = [
+        f"validate_screenshot_basic_{timestamp}.png",
+        f"validate_screenshot_with_spaces {timestamp}.png",
+        f"validate_screenshot_final_{timestamp}.png"
+    ]
+    
+    print("\nTaking screenshots...")
+    for i, filename in enumerate(screenshots):
+        result = automation.screenshot(filename)
+        print(f"Screenshot {i+1}: {filename} - Result: {result}")
+    
+    # Test invalid cases
+    print("\nTesting edge cases...")
+    
+    # Empty filename
+    result = automation.screenshot("")
+    print(f"Empty filename result: {result}")
+    
+    # Very long filename
+    long_name = "x" * 200 + ".png"
+    result = automation.screenshot(long_name)
+    print(f"Long filename result: {result}")
+    
+    print("\n=== Test Complete ===")
+    print("Check the PNG files to see if they contain visible content.")
+    print("If they're transparent, the headless renderer may not be working correctly.")
+    
+    # List what should be visible
+    print("\nExpected content:")
+    print("- Light gray background (200, 200, 200)")
+    print("- Red frame with white outline at (50, 50)")
+    print("- Green frame with black outline at (400, 50)")
+    print("- Blue frame with yellow outline at (50, 300)")
+    print("- White, black, and yellow text labels")
+    
+    sys.exit(0)
+
+# Run the test immediately
+test_screenshot_validation()