Add cookbook examples with updated callback signatures for #229, #230

Cookbook structure:
- lib/: Reusable component library (Button, StatBar, AnimationChain, etc.)
- primitives/: Demo apps for individual components
- features/: Demo apps for complex features (animation chaining, shaders)
- apps/: Complete mini-applications (calculator, dialogue system)
- automation/: Screenshot capture utilities

API signature updates applied:
- on_enter/on_exit/on_move callbacks now only receive (pos) per #230
- on_cell_enter/on_cell_exit callbacks only receive (cell_pos) per #230
- Animation chain library uses Timer-based sequencing (unaffected by #229)

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

tests/cookbook/__init__.py

@@ -0,0 +1,15 @@
+# McRogueFace Cookbook - Widget Standard Library and Demos
+"""
+A comprehensive collection of reusable UI widgets and interactive demos
+showcasing McRogueFace capabilities.
+
+Usage:
+    # Interactive menu
+    cd build && ./mcrogueface ../tests/cookbook/cookbook_main.py
+
+    # Run specific demo
+    cd build && ./mcrogueface ../tests/cookbook/primitives/demo_button.py
+
+    # Generate screenshots (headless)
+    cd build && ./mcrogueface --headless --exec ../tests/cookbook/run_screenshots.py
+"""