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/dijkstra_test.py

@@ -128,12 +128,12 @@ grid.position = (50, 50)
 grid.size = (500, 300)
 
 # Add title
-title = mcrfpy.Caption("Dijkstra Pathfinding Test", 200, 10)
+title = mcrfpy.Caption(pos=(200, 10), text="Dijkstra Pathfinding Test")
 title.fill_color = mcrfpy.Color(255, 255, 255)
 ui.append(title)
 
 # Add legend
-legend = mcrfpy.Caption("Red=Entity1  Green=Entity2  Blue=Entity3  Cyan=Path 1→3", 50, 360)
+legend = mcrfpy.Caption(pos=(50, 360), text="Red=Entity1  Green=Entity2  Blue=Entity3  Cyan=Path 1→3")
 legend.fill_color = mcrfpy.Color(180, 180, 180)
 ui.append(legend)