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/simple_timer_screenshot_test.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+"""Simplified test to verify timer-based screenshots work"""
+import mcrfpy
+from mcrfpy import automation
+
+# Counter to track timer calls
+call_count = 0
+
+def take_screenshot_and_exit():
+    """Timer callback that takes screenshot then exits"""
+    global call_count
+    call_count += 1
+    
+    print(f"\nTimer callback fired! (call #{call_count})")
+    
+    # Take screenshot
+    filename = f"timer_screenshot_test_{call_count}.png"
+    result = automation.screenshot(filename)
+    print(f"Screenshot result: {result} -> {filename}")
+    
+    # Exit after first call
+    if call_count >= 1:
+        print("Exiting game...")
+        mcrfpy.exit()
+
+# Set up a simple scene
+print("Creating test scene...")
+mcrfpy.createScene("test")
+mcrfpy.setScene("test")
+ui = mcrfpy.sceneUI("test")
+
+# Add visible content - a white frame on default background
+frame = mcrfpy.Frame(100, 100, 200, 200,
+                    fill_color=mcrfpy.Color(255, 255, 255))
+ui.append(frame)
+
+print("Setting timer to fire in 100ms...")
+mcrfpy.setTimer("screenshot_timer", take_screenshot_and_exit, 100)
+
+print("Setup complete. Game loop starting...")