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/debug_render_test.py

@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+"""Debug rendering to find why screenshots are transparent"""
+import mcrfpy
+from mcrfpy import automation
+import sys
+
+# Check if we're in headless mode
+print("=== Debug Render Test ===")
+print(f"Module loaded: {mcrfpy}")
+print(f"Automation available: {'automation' in dir(mcrfpy)}")
+
+# Try to understand the scene state
+print("\nCreating and checking scene...")
+mcrfpy.createScene("debug_scene")
+mcrfpy.setScene("debug_scene")
+current = mcrfpy.currentScene()
+print(f"Current scene: {current}")
+
+# Get UI collection
+ui = mcrfpy.sceneUI("debug_scene")
+print(f"UI collection type: {type(ui)}")
+print(f"Initial UI elements: {len(ui)}")
+
+# Add a simple frame
+frame = mcrfpy.Frame(0, 0, 100, 100, 
+                    fill_color=mcrfpy.Color(255, 255, 255))
+ui.append(frame)
+print(f"After adding frame: {len(ui)} elements")
+
+# Check if the issue is with timing
+print("\nTaking immediate screenshot...")
+result1 = automation.screenshot("debug_immediate.png")
+print(f"Immediate screenshot result: {result1}")
+
+# Maybe we need to let the engine process the frame?
+# In headless mode with --exec, the game loop might not be running
+print("\nNote: In --exec mode, the game loop doesn't run continuously.")
+print("This might prevent rendering from occurring.")
+
+# Let's also check what happens with multiple screenshots
+for i in range(3):
+    result = automation.screenshot(f"debug_multi_{i}.png")
+    print(f"Screenshot {i}: {result}")
+
+print("\nConclusion: The issue appears to be that in --exec mode,")
+print("the render loop never runs, so nothing is drawn to the RenderTexture.")
+print("The screenshot captures an uninitialized/unrendered texture.")
+
+sys.exit(0)