feat: Add dirty flag propagation to all UIDrawables and expand metrics API (#144, #104)

- Add markDirty() calls to setProperty() methods in:
  - UISprite: position, scale, sprite_index changes
  - UICaption: position, font_size, colors, text changes
  - UIGrid: position, size, center, zoom, color changes
  - UILine: thickness, position, endpoints, color changes
  - UICircle: radius, position, colors changes
  - UIArc: radius, angles, position, color changes
  - UIEntity: position changes propagate to parent grid

- Expand getMetrics() Python API to include detailed timing breakdown:
  - grid_render_time, entity_render_time, fov_overlay_time
  - python_time, animation_time
  - grid_cells_rendered, entities_rendered, total_entities

- Add comprehensive benchmark suite (tests/benchmarks/benchmark_suite.py):
  - 6 scenarios: empty, static UI, animated UI, mixed, deep hierarchy, grid stress
  - Automated metrics collection and performance assessment
  - Timing breakdown percentages

This enables proper dirty flag propagation for the upcoming texture caching
system (#144) and provides infrastructure for performance benchmarking (#104).

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

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

src/UICaption.cpp

@@ -471,71 +471,84 @@ bool UICaption::setProperty(const std::string& name, float value) {
     if (name == "x") {
         position.x = value;
         text.setPosition(position);  // Keep text in sync
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     else if (name == "y") {
         position.y = value;
         text.setPosition(position);  // Keep text in sync
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     else if (name == "font_size" || name == "size") { // Support both for backward compatibility
         text.setCharacterSize(static_cast<unsigned int>(value));
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "outline") {
         text.setOutlineThickness(value);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "fill_color.r") {
         auto color = text.getFillColor();
         color.r = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setFillColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "fill_color.g") {
         auto color = text.getFillColor();
         color.g = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setFillColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "fill_color.b") {
         auto color = text.getFillColor();
         color.b = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setFillColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "fill_color.a") {
         auto color = text.getFillColor();
         color.a = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setFillColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "outline_color.r") {
         auto color = text.getOutlineColor();
         color.r = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setOutlineColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "outline_color.g") {
         auto color = text.getOutlineColor();
         color.g = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setOutlineColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "outline_color.b") {
         auto color = text.getOutlineColor();
         color.b = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setOutlineColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "outline_color.a") {
         auto color = text.getOutlineColor();
         color.a = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setOutlineColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "z_index") {
         z_index = static_cast<int>(value);
+        markDirty();  // #144 - Z-order change affects parent
         return true;
     }
     return false;
@@ -544,10 +557,12 @@ bool UICaption::setProperty(const std::string& name, float value) {
 bool UICaption::setProperty(const std::string& name, const sf::Color& value) {
     if (name == "fill_color") {
         text.setFillColor(value);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "outline_color") {
         text.setOutlineColor(value);
+        markDirty();  // #144 - Content change
         return true;
     }
     return false;
@@ -556,6 +571,7 @@ bool UICaption::setProperty(const std::string& name, const sf::Color& value) {
 bool UICaption::setProperty(const std::string& name, const std::string& value) {
     if (name == "text") {
         text.setString(value);
+        markDirty();  // #144 - Content change
         return true;
     }
     return false;