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_quickstart_simple_scene.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+"""Test for quickstart.md 'Simple Test Scene' example.
+
+Original (DEPRECATED - lines 48-74):
+    mcrfpy.createScene("test")
+    grid = mcrfpy.Grid(20, 15, texture, (10, 10), (800, 600))
+    ui = mcrfpy.sceneUI("test")
+    mcrfpy.setScene("test")
+    mcrfpy.keypressScene(move_around)
+
+Modern equivalent below.
+"""
+import mcrfpy
+from mcrfpy import automation
+import sys
+
+# Create scene using modern API
+scene = mcrfpy.Scene("test")
+scene.activate()
+mcrfpy.step(0.01)  # Initialize
+
+# Load texture
+texture = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+
+# Create grid using modern keyword API
+grid = mcrfpy.Grid(
+    grid_size=(20, 15),
+    texture=texture,
+    pos=(10, 10),
+    size=(800, 600)
+)
+
+# Add to scene's children (not sceneUI)
+scene.children.append(grid)
+
+# Add keyboard controls using modern API
+def move_around(key, state):
+    if state == "start":
+        print(f"You pressed {key}")
+
+scene.on_key = move_around
+
+# Render and screenshot
+mcrfpy.step(0.1)
+automation.screenshot("/opt/goblincorps/repos/McRogueFace/tests/docs/screenshots/quickstart_simple_scene.png")
+
+print("PASS - quickstart simple scene")
+sys.exit(0)