fix: Update test files to use current API patterns

Migrates test suite to current API:
- Frame(x, y, w, h) → Frame(pos=(x, y), size=(w, h))
- Caption("text", x, y) → Caption(pos=(x, y), text="text")
- caption.size → caption.font_size
- Entity(x, y, ...) → Entity((x, y), ...)
- Grid(w, h, ...) → Grid(grid_size=(w, h), ...)
- cell.color → ColorLayer system

Tests now serve as valid API usage examples.

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

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

tests/unit/test_headless_modes.py

@@ -10,13 +10,13 @@ ui = mcrfpy.sceneUI("headless_test")
 mcrfpy.setScene("headless_test")
 
 # Create a visible indicator
-frame = mcrfpy.Frame(200, 200, 400, 200)
-frame.fill_color = (100, 200, 100, 255)
+frame = mcrfpy.Frame(pos=(200, 200), size=(400, 200))
+frame.fill_color = mcrfpy.Color(100, 200, 100, 255)
 ui.append(frame)
 
-caption = mcrfpy.Caption((400, 300), "If you see this, windowed mode is working!", mcrfpy.default_font)
-caption.size = 24
-caption.fill_color = (255, 255, 255)
+caption = mcrfpy.Caption(pos=(400, 300), text="If you see this, windowed mode is working!")
+caption.font_size = 24
+caption.fill_color = mcrfpy.Color(255, 255, 255)
 ui.append(caption)
 
 print("Script started. Window should appear unless --headless was specified.")