fix(renderer): mesh collider source positions in render space for skinned meshes

Skinned meshes keep vertices in raw mesh space (bakeTransform=false);
rendering transforms them via bind palette (global(bone) x invBind, folds
FBX unit scale). Physics MeshShape/ConvexHull and the mesh bounding sphere
consumed the raw positions directly -> M1911 hull measured ~10x the visual
size. ParseFromDisk now bakes bind-palette-skinned positions per vertex
(same formula as the skinning shader) into ParsedMesh::cpuPositions; Mesh
uses them for m_CpuPositions and bounds. GPU vertex data and rendering are
untouched.

Engine/src/Renderer/Model.cpp

@@ -238,6 +238,42 @@ ParsedModel Model::ParseFromDisk(const std::string& path)
                             bone.name);
             }
         }
+
+        // 蒙皮 mesh 的 CPU 位置副本换算到渲染空间：渲染 = palette(t)×raw
+        //（palette = global(bone)×invBind，与 shader 同式），物理/包围球取
+        // 绑定姿态。FBX 的单位换算折在骨骼链上（bind palette ≠ I），直接
+        // 用 raw 会让物理凸包大一个数量级（M1911 实测 10×）
+        if (!out.bones.empty()) {
+            std::vector<glm::mat4> globals(out.nodes.size());
+            for (size_t i = 0; i < out.nodes.size(); ++i) {
+                globals[i] = out.nodes[i].parent < 0
+                    ? out.nodes[i].localTransform
+                    : globals[out.nodes[i].parent] * out.nodes[i].localTransform;
+            }
+            std::vector<glm::mat4> bindPalette(out.bones.size());
+            for (size_t b = 0; b < out.bones.size(); ++b) {
+                bindPalette[b] = globals[out.bones[b].nodeIdx]
+                                 * out.bones[b].invBind;
+            }
+            for (auto& pm : out.meshes) {
+                if (!pm.skinned) continue;
+                pm.cpuPositions.resize(pm.vertices.size());
+                for (size_t v = 0; v < pm.vertices.size(); ++v) {
+                    const Vertex& vert = pm.vertices[v];
+                    glm::vec3 p(0.0f);
+                    f32 wsum = 0.0f;
+                    for (int k = 0; k < 4; ++k) {
+                        const f32 w = vert.weights[k];
+                        if (w <= 0.0f) continue;
+                        p += w * glm::vec3(bindPalette[vert.boneIds[k]]
+                                           * glm::vec4(vert.position, 1.0f));
+                        wsum += w;
+                    }
+                    // 零权重顶点（shader 侧塌到原点）物理侧保留原始位置兜底
+                    pm.cpuPositions[v] = wsum > 1e-6f ? p : vert.position;
+                }
+            }
+        }
     }
 
     ENGINE_INFO("Model parsed: {} ({} meshes, {} bones, {} anims)",
@@ -383,7 +419,8 @@ Scope<Model> Model::FromParsed(Device& device, MemoryAllocator& allocator,
     for (auto& pm : parsed.meshes) {
         Material* mat = model->GetOrCreateMaterial(pm.texPaths.data(), pm.params);
         model->m_Meshes.push_back(CreateScope<Mesh>(
-            device, allocator, pm.vertices, pm.lods, mat));
+            device, allocator, pm.vertices, pm.lods, mat,
+            pm.cpuPositions.empty() ? nullptr : &pm.cpuPositions));
     }
     ENGINE_INFO("Model loaded: {} ({} meshes, {} textures)",
                 parsed.path, model->m_Meshes.size(), model->m_TextureCache.size());
@@ -406,7 +443,8 @@ void Model::LoadModel(const std::string& path)
     for (auto& pm : parsed.meshes) {
         Material* mat = GetOrCreateMaterial(pm.texPaths.data(), pm.params);
         m_Meshes.push_back(CreateScope<Mesh>(
-            m_Device, m_Allocator, pm.vertices, pm.lods, mat));
+            m_Device, m_Allocator, pm.vertices, pm.lods, mat,
+            pm.cpuPositions.empty() ? nullptr : &pm.cpuPositions));
     }
     ENGINE_INFO("Model loaded: {} ({} meshes, {} textures)",
                 path, m_Meshes.size(), m_TextureCache.size());
@@ -577,6 +615,7 @@ ParsedMesh Model::ProcessMesh(const aiMesh* mesh, const aiScene* scene,
 
     // 骨骼权重灌顶点（无骨骼 mesh 顶点保持默认 idx0/w1 → identity 直通）
     CollectMeshBones(mesh, vertices, bones, boneSlots);
+    out.skinned = hasBones;
 
     for (u32 i = 0; i < mesh->mNumFaces; ++i) {
         aiFace face = mesh->mFaces[i];