Update test demos for new Python API and entity system

- Update all text input demos to use new Entity constructor signature
- Fix pathfinding showcase to work with new entity position handling
- Remove entity_waypoints tracking in favor of simplified movement
- Delete obsolete exhaustive_api_demo.py (superseded by newer demos)
- Adjust entity creation calls to match Entity((x, y), texture, sprite_index) pattern

All demos now properly demonstrate the updated API while maintaining their
original functionality for showcasing engine features.

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

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

tests/demos/text_input_widget.py

@@ -95,8 +95,7 @@ class TextInput:
             self.label_text = mcrfpy.Caption(
                 self.x - 5, 
                 self.y - self.font_size - 5,
-                self.label,
-                font_size=self.font_size
+                self.label
             )
             self.label_text.color = (255, 255, 255, 255)
         
@@ -104,8 +103,7 @@ class TextInput:
         self.text_display = mcrfpy.Caption(
             self.x + 4,
             self.y + 4,
-            "",
-            font_size=self.font_size
+            ""
         )
         self.text_display.color = (0, 0, 0, 255)
         
@@ -227,12 +225,12 @@ def create_demo():
     scene.append(bg)
     
     # Title
-    title = mcrfpy.Caption(10, 10, "Text Input Widget Demo", font_size=24)
+    title = mcrfpy.Caption(10, 10, "Text Input Widget Demo")
     title.color = (255, 255, 255, 255)
     scene.append(title)
     
     # Instructions
-    instructions = mcrfpy.Caption(10, 50, "Click to focus, Tab to switch fields, Type to enter text", font_size=14)
+    instructions = mcrfpy.Caption(10, 50, "Click to focus, Tab to switch fields, Type to enter text")
     instructions.color = (200, 200, 200, 255)
     scene.append(instructions)
     
@@ -276,7 +274,7 @@ def create_demo():
     fields.append(comment_input)
     
     # Result display
-    result_text = mcrfpy.Caption(50, 320, "Type in the fields above...", font_size=14)
+    result_text = mcrfpy.Caption(50, 320, "Type in the fields above...")
     result_text.color = (150, 255, 150, 255)
     scene.append(result_text)