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/debug_visibility.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+"""Debug visibility crash"""
+
+import mcrfpy
+import sys
+
+print("Debug visibility...")
+
+# Create scene and grid
+mcrfpy.createScene("debug")
+grid = mcrfpy.Grid(grid_x=5, grid_y=5)
+
+# Initialize grid
+print("Initializing grid...")
+for y in range(5):
+    for x in range(5):
+        cell = grid.at(x, y)
+        cell.walkable = True
+        cell.transparent = True
+
+# Create entity
+print("Creating entity...")
+entity = mcrfpy.Entity(2, 2)
+entity.sprite_index = 64
+grid.entities.append(entity)
+print(f"Entity at ({entity.x}, {entity.y})")
+
+# Check gridstate
+print(f"\nGridstate length: {len(entity.gridstate)}")
+print(f"Expected: {5 * 5}")
+
+# Try to access gridstate
+print("\nChecking gridstate access...")
+try:
+    if len(entity.gridstate) > 0:
+        state = entity.gridstate[0]
+        print(f"First state: visible={state.visible}, discovered={state.discovered}")
+except Exception as e:
+    print(f"Error accessing gridstate: {e}")
+
+# Try update_visibility
+print("\nTrying update_visibility...")
+try:
+    entity.update_visibility()
+    print("update_visibility succeeded")
+except Exception as e:
+    print(f"Error in update_visibility: {e}")
+
+# Try perspective
+print("\nTesting perspective...")
+print(f"Initial perspective: {grid.perspective}")
+try:
+    grid.perspective = 0
+    print(f"Set perspective to 0: {grid.perspective}")
+except Exception as e:
+    print(f"Error setting perspective: {e}")
+
+print("\nTest complete")
+sys.exit(0)