Add Game-to-API Bridge for external client integration

Implements a general-purpose HTTP API that exposes McRogueFace games
to external clients (LLMs, accessibility tools, Twitch integrations,
testing harnesses).

API endpoints:
- GET /scene - Full scene graph with all UI elements
- GET /affordances - Interactive elements with semantic labels
- GET /screenshot - PNG screenshot (binary or base64)
- GET /metadata - Game metadata for LLM context
- GET /wait - Long-poll for state changes
- POST /input - Inject clicks, keys, or affordance clicks

Key features:
- Automatic affordance detection from Frame+Caption+on_click patterns
- Label extraction from caption text with fallback to element.name
- Thread-safe scene access via mcrfpy.lock()
- Fuzzy label matching for click_affordance
- Full input injection via mcrfpy.automation

Usage: from api import start_server; start_server(8765)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/api/run_api_server.py

@@ -0,0 +1,84 @@
+#!/usr/bin/env python3
+"""Simple script to start the McRogueFace Game API server.
+
+Run with: cd build && ./mcrogueface --exec ../tests/api/run_api_server.py
+
+Then test with:
+    curl http://localhost:8765/health
+    curl http://localhost:8765/scene
+    curl http://localhost:8765/affordances
+"""
+
+import sys
+sys.path.insert(0, '../src/scripts')
+
+import mcrfpy
+
+print("Creating test scene...", flush=True)
+
+# Create a simple test scene
+scene = mcrfpy.Scene("test")
+ui = scene.children
+
+font = mcrfpy.Font("assets/JetbrainsMono.ttf")
+
+# Title
+title = mcrfpy.Caption(text="API Test Scene", pos=(50, 20), font=font, fill_color=(255, 255, 0))
+title.font_size = 24
+ui.append(title)
+
+# A clickable button
+button = mcrfpy.Frame(pos=(50, 80), size=(200, 50), fill_color=(64, 64, 128))
+button.name = "test_button"
+button.on_click = lambda pos, btn, action: print(f"Button clicked: {action}", flush=True)
+button_text = mcrfpy.Caption(text="Click Me", pos=(50, 10), font=font, fill_color=(255, 255, 255))
+button.children.append(button_text)
+ui.append(button)
+
+# A second button
+button2 = mcrfpy.Frame(pos=(50, 150), size=(200, 50), fill_color=(64, 128, 64))
+button2.name = "settings_button"
+button2.on_click = lambda pos, btn, action: print(f"Settings clicked: {action}", flush=True)
+button2_text = mcrfpy.Caption(text="Settings", pos=(50, 10), font=font, fill_color=(255, 255, 255))
+button2.children.append(button2_text)
+ui.append(button2)
+
+# Status text
+status = mcrfpy.Caption(text="API Server running on http://localhost:8765", pos=(50, 230), font=font, fill_color=(128, 255, 128))
+ui.append(status)
+
+status2 = mcrfpy.Caption(text="Press ESC to exit", pos=(50, 260), font=font, fill_color=(200, 200, 200))
+ui.append(status2)
+
+mcrfpy.current_scene = scene
+
+print("Starting API server...", flush=True)
+
+# Start the API server
+from api import start_server
+server = start_server(8765)
+
+print("", flush=True)
+print("=" * 50, flush=True)
+print("API Server is ready!", flush=True)
+print("", flush=True)
+print("Test endpoints:", flush=True)
+print("  curl http://localhost:8765/health", flush=True)
+print("  curl http://localhost:8765/scene", flush=True)
+print("  curl http://localhost:8765/affordances", flush=True)
+print("  curl http://localhost:8765/metadata", flush=True)
+print("  curl http://localhost:8765/screenshot?format=base64 | jq -r .image", flush=True)
+print("", flush=True)
+print("Input examples:", flush=True)
+print('  curl -X POST -H "Content-Type: application/json" -d \'{"action":"key","key":"W"}\' http://localhost:8765/input', flush=True)
+print('  curl -X POST -H "Content-Type: application/json" -d \'{"action":"click","x":150,"y":100}\' http://localhost:8765/input', flush=True)
+print("=" * 50, flush=True)
+print("", flush=True)
+
+# Key handler
+def on_key(key, action):
+    if key == mcrfpy.Key.ESCAPE and action == mcrfpy.InputState.PRESSED:
+        print("Exiting...", flush=True)
+        mcrfpy.exit()
+
+scene.on_key = on_key