Environment settings become scene entities (UE Skybox/SkyLight semantics)

Skybox/SkyLight are now Actor-carried components instead of resident
global settings, matching UE where SkyAtmosphere/SkyLight/fog are
Actors added from Place Actors and configured in Details.

- New SkyboxComponent (active + envPath asset slot) and SkyLightComponent
  (active + ambientColor); first-active entity wins per frame
- SceneRenderer collects env from components into FrameSceneData
  (DrawSkybox/envPath/ambient); Renderer performs delta sync - env
  reloads only when the resolved path changes, neutral fallback when
  empty or unloadable
- App-side env plumbing removed: kEnvPaths table and getEnvIndex/
  setEnvIndex callbacks deleted; StatsPanel keeps ClearColor + debug
  view, env params move to Details
- Serializer: scene-level Settings stores ClearColor only; env
  components serialize per entity; legacy v1 scenes (Environment header
  + Settings.AmbientColor/DrawSkybox) auto-migrate into an Environment
  entity on load for visual parity
- Inspector: Skybox/Sky Light sections with .hdr asset slot dropdown
  and Add Component entries; Outliner "+ Create" popup offers
  Empty/Light/Camera/Environment

App/editor/InspectorPanel.cpp

@@ -58,6 +58,39 @@ namespace
         return s_Files;
     }
 
+    // 递归收集 assets/ 下环境贴图（.hdr，Skybox 资产槽用；会话级缓存同上）
+    const std::vector<std::string>& AssetEnvFiles()
+    {
+        static std::vector<std::string> s_Files;
+        static bool s_Cached = false;
+        if (!s_Cached)
+        {
+            s_Cached = true;
+            namespace fs = std::filesystem;
+            if (fs::exists("assets"))
+            {
+                for (const auto& entry :
+                     fs::recursive_directory_iterator("assets"))
+                {
+                    if (!entry.is_regular_file())
+                    {
+                        continue;
+                    }
+                    std::string ext = entry.path().extension().string();
+                    std::transform(ext.begin(), ext.end(), ext.begin(),
+                                   [](unsigned char c)
+                                   { return std::tolower(c); });
+                    if (ext == ".hdr")
+                    {
+                        s_Files.push_back(entry.path().generic_string());
+                    }
+                }
+                std::sort(s_Files.begin(), s_Files.end());
+            }
+        }
+        return s_Files;
+    }
+
     // InputText 需要 char 缓冲；提交时写回 std::string
     bool InputTextString(const char* label, std::string& str)
     {
@@ -198,6 +231,9 @@ void InspectorPanel::Draw(const EditorContext& ctx, entt::entity selected)
         menuItem(static_cast<Engine::ECS::MeshRendererComponent*>(nullptr),
                  "Mesh Renderer");
         menuItem(static_cast<Engine::ECS::LightComponent*>(nullptr), "Light");
+        menuItem(static_cast<Engine::ECS::SkyboxComponent*>(nullptr), "Skybox");
+        menuItem(static_cast<Engine::ECS::SkyLightComponent*>(nullptr),
+                 "Sky Light");
         menuItem(static_cast<Engine::ECS::CameraComponent*>(nullptr), "Camera");
         menuItem(static_cast<Engine::ECS::AnimationComponent*>(nullptr), "Animation");
         menuItem(static_cast<Engine::ECS::NameComponent*>(nullptr), "Name");
@@ -417,6 +453,78 @@ void InspectorPanel::Draw(const EditorContext& ctx, entt::entity selected)
         }
     }
 
+    // ---- Skybox（UE Skybox Actor 语义：环境贴图 = 实体资产槽）----
+    if (auto* sb = reg.try_get<Engine::ECS::SkyboxComponent>(selected))
+    {
+        bool removeSb = false;
+        if (ComponentHeader("Skybox", &sb->active, true, &removeSb))
+        {
+            if (!sb->active)
+            {
+                ImGui::BeginDisabled(true);
+            }
+            // 环境贴图资产槽（模型槽同款：下拉列 assets/ 下 .hdr，选中
+            // 即加载；空 = 无环境，只露清屏色）。渲染侧由 Renderer 按
+            // 帧数据差量同步（路径变化才重载），此处零额外同步
+            {
+                const auto& s_EnvFiles = AssetEnvFiles();
+                std::vector<const char*> opts;
+                opts.push_back("<none>");
+                for (const auto& f : s_EnvFiles)
+                {
+                    opts.push_back(f.c_str());
+                }
+                int sel = 0;
+                for (size_t k = 0; k < s_EnvFiles.size(); ++k)
+                {
+                    if (s_EnvFiles[k] == sb->envPath)
+                    {
+                        sel = static_cast<int>(k) + 1;
+                    }
+                }
+                ImGui::SetNextItemWidth(-1.0f);
+                if (ImGui::Combo("##env_slot", &sel, opts.data(),
+                                 static_cast<int>(opts.size())))
+                {
+                    sb->envPath = (sel <= 0)
+                        ? std::string{}
+                        : s_EnvFiles[static_cast<size_t>(sel) - 1];
+                }
+                ImGui::TextDisabled("(empty = clear color only)");
+            }
+            if (!sb->active)
+            {
+                ImGui::EndDisabled();
+            }
+        }
+        if (removeSb)
+        {
+            reg.remove<Engine::ECS::SkyboxComponent>(selected);
+        }
+    }
+
+    // ---- SkyLight（UE SkyLight 语义：全局环境光）----
+    if (auto* sl = reg.try_get<Engine::ECS::SkyLightComponent>(selected))
+    {
+        bool removeSl = false;
+        if (ComponentHeader("Sky Light", &sl->active, true, &removeSl))
+        {
+            if (!sl->active)
+            {
+                ImGui::BeginDisabled(true);
+            }
+            ImGui::ColorEdit4("ambient", &sl->ambientColor.x);
+            if (!sl->active)
+            {
+                ImGui::EndDisabled();
+            }
+        }
+        if (removeSl)
+        {
+            reg.remove<Engine::ECS::SkyLightComponent>(selected);
+        }
+    }
+
     // ---- Camera ----
     if (auto* cam = reg.try_get<Engine::ECS::CameraComponent>(selected))
     {