Add API verification test suite and documentation

tests/docs/:
- API_FINDINGS.md: Comprehensive migration guide from deprecated to modern API
- test_*.py: 9 executable tests verifying actual runtime behavior
- screenshots/: Visual verification of working examples

tests/conftest.py:
- Add 'docs' and 'demo' to pytest collection paths

Key findings documented:
- Entity uses grid_pos= not pos=
- Scene API: Scene() + activate() replaces createScene/setScene
- scene.children replaces sceneUI()
- scene.on_key replaces keypressScene()
- mcrfpy.current_scene (property) replaces currentScene() (function)
- Timer callback signature: (timer, runtime)
- Opacity animation does NOT work on Frame (documented bug)

🤖 Generated with Claude Code (https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

tests/docs/test_defaults.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python3
+"""Test mcrfpy default resources."""
+import mcrfpy
+import sys
+
+scene = mcrfpy.Scene("test")
+scene.activate()
+mcrfpy.step(0.01)
+
+print("Checking mcrfpy defaults:")
+
+try:
+    dt = mcrfpy.default_texture
+    print(f"  default_texture = {dt}")
+except AttributeError as e:
+    print(f"  default_texture: NOT FOUND")
+
+try:
+    df = mcrfpy.default_font
+    print(f"  default_font = {df}")
+except AttributeError as e:
+    print(f"  default_font: NOT FOUND")
+
+# Also check what other module-level attributes exist
+print("\nAll mcrfpy attributes starting with 'default':")
+for attr in dir(mcrfpy):
+    if 'default' in attr.lower():
+        print(f"  {attr}")
+
+sys.exit(0)