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/api_setScene_currentScene_test.py

@@ -0,0 +1,44 @@
+#!/usr/bin/env python3
+"""Test for mcrfpy.setScene() and currentScene() methods"""
+import mcrfpy
+
+print("Starting setScene/currentScene test...")
+
+# Create test scenes first
+scenes = ["scene_A", "scene_B", "scene_C"]
+for scene in scenes:
+    mcrfpy.createScene(scene)
+    print(f"Created scene: {scene}")
+
+results = []
+
+# Test switching between scenes
+for scene in scenes:
+    try:
+        mcrfpy.setScene(scene)
+        current = mcrfpy.currentScene()
+        if current == scene:
+            results.append(f"✓ setScene/currentScene works for '{scene}'")
+        else:
+            results.append(f"✗ Scene mismatch: set '{scene}', got '{current}'")
+    except Exception as e:
+        results.append(f"✗ Error with scene '{scene}': {e}")
+
+# Test invalid scene - it should not change the current scene
+current_before = mcrfpy.currentScene()
+mcrfpy.setScene("nonexistent_scene")
+current_after = mcrfpy.currentScene()
+if current_before == current_after:
+    results.append(f"✓ setScene correctly ignores nonexistent scene (stayed on '{current_after}')")
+else:
+    results.append(f"✗ Scene changed unexpectedly from '{current_before}' to '{current_after}'")
+
+# Print results
+for result in results:
+    print(result)
+
+# Determine pass/fail
+if all("✓" in r for r in results):
+    print("PASS")
+else:
+    print("FAIL")