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/integration/simple_visibility_test.py

@@ -13,8 +13,8 @@ print("Scene created")
 grid = mcrfpy.Grid(grid_x=5, grid_y=5)
 print("Grid created")
 
-# Create entity without appending
-entity = mcrfpy.Entity(2, 2, grid=grid)
+# Create entity with grid association
+entity = mcrfpy.Entity((2, 2), grid=grid)
 print(f"Entity created at ({entity.x}, {entity.y})")
 
 # Check if gridstate is initialized