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/trace_exec_behavior.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+"""Trace execution behavior to understand the >>> prompt"""
+import mcrfpy
+import sys
+import traceback
+
+print("=== Tracing Execution ===")
+print(f"Python version: {sys.version}")
+print(f"sys.argv: {sys.argv}")
+print(f"__name__: {__name__}")
+
+# Check if we're in interactive mode
+print(f"sys.flags.interactive: {sys.flags.interactive}")
+print(f"sys.flags.inspect: {sys.flags.inspect}")
+
+# Check sys.ps1 (interactive prompt)
+if hasattr(sys, 'ps1'):
+    print(f"sys.ps1 exists: '{sys.ps1}'")
+else:
+    print("sys.ps1 not set (not in interactive mode)")
+
+# Create a simple scene
+mcrfpy.createScene("trace_test")
+mcrfpy.setScene("trace_test")
+print(f"Current scene: {mcrfpy.currentScene()}")
+
+# Set a timer that should fire
+def timer_test():
+    print("\n!!! Timer fired successfully !!!")
+    mcrfpy.delTimer("trace_timer")
+    # Try to exit
+    print("Attempting to exit...")
+    mcrfpy.exit()
+
+print("Setting timer...")
+mcrfpy.setTimer("trace_timer", timer_test, 500)
+
+print("\n=== Script execution complete ===")
+print("If you see >>> after this, Python entered interactive mode")
+print("The game loop should start now...")
+
+# Try to ensure we don't enter interactive mode
+if hasattr(sys, 'ps1'):
+    del sys.ps1
+    
+# Explicitly NOT calling sys.exit() to let the game loop run