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_main_menu.py

@@ -0,0 +1,74 @@
+#!/usr/bin/env python3
+"""Test for quickstart.md 'Main Menu' example.
+
+Original (DEPRECATED - lines 82-125):
+    mcrfpy.createScene("main_menu")
+    ui = mcrfpy.sceneUI("main_menu")
+    bg = mcrfpy.Frame(0, 0, 1024, 768, fill_color=(20, 20, 40))
+    title = mcrfpy.Caption((312, 100), "My Awesome Game", font, fill_color=(255, 255, 100))
+    button_frame.click = start_game
+    mcrfpy.setScene("main_menu")
+
+Modern equivalent below.
+"""
+import mcrfpy
+from mcrfpy import automation
+import sys
+
+# Create scene using modern API
+scene = mcrfpy.Scene("main_menu")
+scene.activate()
+mcrfpy.step(0.01)
+
+# Load font
+font = mcrfpy.Font("assets/JetbrainsMono.ttf")
+
+# Add background using modern Frame API (keyword args)
+bg = mcrfpy.Frame(
+    pos=(0, 0),
+    size=(1024, 768),
+    fill_color=mcrfpy.Color(20, 20, 40)
+)
+scene.children.append(bg)
+
+# Add title using modern Caption API
+title = mcrfpy.Caption(
+    pos=(312, 100),
+    text="My Awesome Game",
+    font=font,
+    fill_color=mcrfpy.Color(255, 255, 100)
+)
+title.font_size = 48
+title.outline = 2
+title.outline_color = mcrfpy.Color(0, 0, 0)
+scene.children.append(title)
+
+# Create button frame
+button_frame = mcrfpy.Frame(
+    pos=(362, 300),
+    size=(300, 80),
+    fill_color=mcrfpy.Color(50, 150, 50)
+)
+
+# Button caption
+button_caption = mcrfpy.Caption(
+    pos=(90, 25),  # Centered in button
+    text="Start Game",
+    fill_color=mcrfpy.Color(255, 255, 255)
+)
+button_caption.font_size = 24
+button_frame.children.append(button_caption)
+
+# Click handler using modern on_click (3 args: x, y, button)
+def start_game(x, y, button):
+    print("Starting the game!")
+
+button_frame.on_click = start_game
+scene.children.append(button_frame)
+
+# Render and screenshot
+mcrfpy.step(0.1)
+automation.screenshot("/opt/goblincorps/repos/McRogueFace/tests/docs/screenshots/quickstart_main_menu.png")
+
+print("PASS - quickstart main menu")
+sys.exit(0)