feat(engine): implement perspective FOV, pathfinding, and GUI text widgets

Major Engine Enhancements:
- Complete FOV (Field of View) system with perspective rendering
  - UIGrid.perspective property for entity-based visibility
  - Three-layer overlay colors (unexplored, explored, visible)
  - Per-entity visibility state tracking
  - Perfect knowledge updates only for explored areas

- Advanced Pathfinding Integration
  - A* pathfinding implementation in UIGrid
  - Entity.path_to() method for direct pathfinding
  - Dijkstra maps for multi-target pathfinding
  - Path caching for performance optimization

- GUI Text Input Widgets
  - TextInputWidget class with cursor, selection, scrolling
  - Improved widget with proper text rendering and input handling
  - Example showcase of multiple text input fields
  - Foundation for in-game console and chat systems

- Performance & Architecture Improvements
  - PyTexture copy operations optimized
  - GameEngine update cycle refined
  - UIEntity property handling enhanced
  - UITestScene modernized

Test Suite:
- Interactive visibility demos showing FOV in action
- Pathfinding comparison (A* vs Dijkstra)
- Debug utilities for visibility and empty path handling
- Sizzle reel demo combining pathfinding and vision
- Multiple text input test scenarios

This commit brings McRogueFace closer to a complete roguelike engine
with essential features like line-of-sight, intelligent pathfinding,
and interactive text input capabilities.

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

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

tests/simple_visibility_test.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python3
+"""Simple visibility test without entity append"""
+
+import mcrfpy
+import sys
+
+print("Simple visibility test...")
+
+# Create scene and grid
+mcrfpy.createScene("simple")
+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)
+print(f"Entity created at ({entity.x}, {entity.y})")
+
+# Check if gridstate is initialized
+print(f"Gridstate length: {len(entity.gridstate)}")
+
+# Try to access at method
+try:
+    state = entity.at(0, 0)
+    print(f"at(0,0) returned: {state}")
+    print(f"visible: {state.visible}, discovered: {state.discovered}")
+except Exception as e:
+    print(f"Error in at(): {e}")
+
+# Try update_visibility
+try:
+    entity.update_visibility()
+    print("update_visibility() succeeded")
+except Exception as e:
+    print(f"Error in update_visibility(): {e}")
+
+print("Test complete")
+sys.exit(0)