feat: Refactor editor structure and enhance multi-session support

- Moved `menu_builder.cc` to a new `ui` directory for better organization.
- Updated `EditorManager` to generate unique ImGui IDs for multi-session support, ensuring separate window handling.
- Added session ID management in `EditorContext` for improved child panel identification.
- Introduced a new `MenuBuilder` class for streamlined ImGui menu creation, enhancing UI maintainability.

src/app/editor/ui/menu_builder.cc

@@ -0,0 +1,187 @@
+#include "app/editor/ui/menu_builder.h"
+
+#include "absl/strings/str_cat.h"
+
+namespace yaze {
+namespace editor {
+
+MenuBuilder& MenuBuilder::BeginMenu(const char* label, const char* icon) {
+  Menu menu;
+  menu.label = label;
+  if (icon) {
+    menu.icon = icon;
+  }
+  menus_.push_back(menu);
+  current_menu_ = &menus_.back();
+  return *this;
+}
+
+MenuBuilder& MenuBuilder::BeginSubMenu(const char* label, const char* icon,
+                                       EnabledCheck enabled) {
+  if (!current_menu_) return *this;
+  
+  MenuItem item;
+  item.type = MenuItem::Type::kSubMenuBegin;
+  item.label = label;
+  if (icon) {
+    item.icon = icon;
+  }
+  item.enabled = enabled;
+  current_menu_->items.push_back(item);
+  return *this;
+}
+
+MenuBuilder& MenuBuilder::EndMenu() {
+  if (!current_menu_) return *this;
+  
+  // Check if we're ending a submenu or top-level menu
+  bool is_submenu = false;
+  for (auto it = current_menu_->items.rbegin(); 
+       it != current_menu_->items.rend(); ++it) {
+    if (it->type == MenuItem::Type::kSubMenuBegin) {
+      is_submenu = true;
+      break;
+    } else if (it->type == MenuItem::Type::kSubMenuEnd) {
+      break;
+    }
+  }
+  
+  if (is_submenu) {
+    MenuItem item;
+    item.type = MenuItem::Type::kSubMenuEnd;
+    current_menu_->items.push_back(item);
+  } else {
+    current_menu_ = nullptr;
+  }
+  
+  return *this;
+}
+
+MenuBuilder& MenuBuilder::Item(const char* label, const char* icon,
+                               Callback callback, const char* shortcut,
+                               EnabledCheck enabled, EnabledCheck checked) {
+  if (!current_menu_) return *this;
+  
+  MenuItem item;
+  item.type = MenuItem::Type::kItem;
+  item.label = label;
+  if (icon) {
+    item.icon = icon;
+  }
+  if (shortcut) {
+    item.shortcut = shortcut;
+  }
+  item.callback = callback;
+  item.enabled = enabled;
+  item.checked = checked;
+  current_menu_->items.push_back(item);
+  return *this;
+}
+
+MenuBuilder& MenuBuilder::Item(const char* label, Callback callback,
+                               const char* shortcut, EnabledCheck enabled) {
+  return Item(label, nullptr, callback, shortcut, enabled, nullptr);
+}
+
+MenuBuilder& MenuBuilder::Separator() {
+  if (!current_menu_) return *this;
+  
+  MenuItem item;
+  item.type = MenuItem::Type::kSeparator;
+  current_menu_->items.push_back(item);
+  return *this;
+}
+
+MenuBuilder& MenuBuilder::DisabledItem(const char* label, const char* icon) {
+  if (!current_menu_) return *this;
+  
+  MenuItem item;
+  item.type = MenuItem::Type::kDisabled;
+  item.label = label;
+  if (icon) {
+    item.icon = icon;
+  }
+  current_menu_->items.push_back(item);
+  return *this;
+}
+
+void MenuBuilder::Draw() {
+  for (const auto& menu : menus_) {
+    std::string menu_label = menu.icon.empty() 
+        ? menu.label 
+        : absl::StrCat(menu.icon, " ", menu.label);
+    
+    if (ImGui::BeginMenu(menu_label.c_str())) {
+      for (const auto& item : menu.items) {
+        DrawMenuItem(item);
+      }
+      ImGui::EndMenu();
+    }
+  }
+}
+
+void MenuBuilder::DrawMenuItem(const MenuItem& item) {
+  switch (item.type) {
+    case MenuItem::Type::kSeparator:
+      ImGui::Separator();
+      break;
+      
+    case MenuItem::Type::kDisabled: {
+      std::string label = item.icon.empty()
+          ? item.label
+          : absl::StrCat(item.icon, " ", item.label);
+      ImGui::BeginDisabled();
+      ImGui::MenuItem(label.c_str(), nullptr, false, false);
+      ImGui::EndDisabled();
+      break;
+    }
+      
+    case MenuItem::Type::kSubMenuBegin: {
+      std::string label = item.icon.empty()
+          ? item.label
+          : absl::StrCat(item.icon, " ", item.label);
+      
+      bool enabled = !item.enabled || item.enabled();
+      if (enabled && ImGui::BeginMenu(label.c_str())) {
+        // Submenu items will be drawn in subsequent calls
+      } else if (!enabled) {
+        ImGui::BeginDisabled();
+        ImGui::MenuItem(label.c_str(), nullptr, false, false);
+        ImGui::EndDisabled();
+      }
+      break;
+    }
+      
+    case MenuItem::Type::kSubMenuEnd:
+      ImGui::EndMenu();
+      break;
+      
+    case MenuItem::Type::kItem: {
+      std::string label = item.icon.empty()
+          ? item.label
+          : absl::StrCat(item.icon, " ", item.label);
+      
+      bool enabled = !item.enabled || item.enabled();
+      bool checked = item.checked && item.checked();
+      
+      const char* shortcut_str = item.shortcut.empty() 
+          ? nullptr 
+          : item.shortcut.c_str();
+      
+      if (ImGui::MenuItem(label.c_str(), shortcut_str, checked, enabled)) {
+        if (item.callback) {
+          item.callback();
+        }
+      }
+      break;
+    }
+  }
+}
+
+void MenuBuilder::Clear() {
+  menus_.clear();
+  current_menu_ = nullptr;
+}
+
+}  // namespace editor
+}  // namespace yaze