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/test_stdin_theory.py

@@ -0,0 +1,32 @@
+#!/usr/bin/env python3
+"""Test if closing stdin prevents the >>> prompt"""
+import mcrfpy
+import sys
+import os
+
+print("=== Testing stdin theory ===")
+print(f"stdin.isatty(): {sys.stdin.isatty()}")
+print(f"stdin fileno: {sys.stdin.fileno()}")
+
+# Set up a basic scene
+mcrfpy.createScene("stdin_test")
+mcrfpy.setScene("stdin_test")
+
+# Try to prevent interactive mode by closing stdin
+print("\nAttempting to prevent interactive mode...")
+try:
+    # Method 1: Close stdin
+    sys.stdin.close()
+    print("Closed sys.stdin")
+except:
+    print("Failed to close sys.stdin")
+
+try:
+    # Method 2: Redirect stdin to /dev/null
+    devnull = open(os.devnull, 'r')
+    os.dup2(devnull.fileno(), 0)
+    print("Redirected stdin to /dev/null")
+except:
+    print("Failed to redirect stdin")
+
+print("\nScript complete. If >>> still appears, the issue is elsewhere.")