feat(body_mesh): Add body mesh separator module with edge dissolution

- Add body_mesh submodule with VRM_OT_separate_non_skin_faces operator
- Add VRM_PT_body_mesh_separator panel for UI integration
- Add utility functions for mesh operations and edge dissolution logic
- Add comprehensive edge dissolution configuration files for all body parts (head, torso, arms, legs, hands) with UV coordinates
- Add test utilities for validating mesh separation operations
- Add .gitignore to exclude Python cache files and test artifacts
- Register body_mesh module in editor package initialization
- Update registration.py to include new body mesh components

editor/body_mesh/panel.py

@@ -0,0 +1,113 @@
+# SPDX-License-Identifier: MIT OR GPL-3.0-or-later
+from collections.abc import Set as AbstractSet
+from typing import TYPE_CHECKING, Optional
+
+from bpy.types import Context, Panel
+
+from .utils import (
+    MaterialInfo,
+    find_body_mesh,
+    get_material_face_count,
+    is_skin_material,
+)
+
+if TYPE_CHECKING:
+    from bpy.types import Object
+
+
+class VRM_PT_body_mesh_separator(Panel):
+    """Body网格分离面板"""
+
+    bl_idname = "VRM_PT_body_mesh_separator"
+    bl_label = "Body Mesh Separator"
+    bl_space_type = "VIEW_3D"
+    bl_region_type = "UI"
+    bl_category = "VRM"
+    bl_options: AbstractSet[str] = set()
+
+    @classmethod
+    def poll(cls, context: Context) -> bool:
+        """检查是否应该显示面板 - 仅在选中包含Body网格的Armature时显示"""
+        armature = cls._get_armature(context)
+        if armature is None:
+            return False
+        body_mesh = find_body_mesh(armature)
+        return body_mesh is not None
+
+    @classmethod
+    def _get_armature(cls, context: Context) -> Optional["Object"]:
+        """获取当前选中的Armature对象"""
+        active_object = context.active_object
+        if active_object is None:
+            return None
+
+        if active_object.type == "ARMATURE":
+            return active_object
+
+        # 如果选中的是网格，检查其父对象是否为Armature
+        if active_object.parent is not None and active_object.parent.type == "ARMATURE":
+            return active_object.parent
+
+        return None
+
+    def draw(self, context: Context) -> None:
+        """绘制面板UI"""
+        layout = self.layout
+        armature = self._get_armature(context)
+
+        if armature is None:
+            layout.label(text="未找到Armature对象", icon="ERROR")
+            return
+
+        body_mesh = find_body_mesh(armature)
+        if body_mesh is None:
+            layout.label(text="未找到Body网格对象", icon="ERROR")
+            return
+
+        mesh_data = body_mesh.data
+        if mesh_data is None:
+            layout.label(text="Body网格数据无效", icon="ERROR")
+            return
+
+        # 显示材质统计信息
+        box = layout.box()
+        box.label(text="材质列表", icon="MATERIAL")
+
+        # 收集材质信息
+        materials_info: list[MaterialInfo] = []
+        for i, material in enumerate(mesh_data.materials):
+            if material is not None:
+                face_count = get_material_face_count(mesh_data, i)
+                is_skin = is_skin_material(material.name)
+                materials_info.append(
+                    MaterialInfo(
+                        name=material.name,
+                        index=i,
+                        face_count=face_count,
+                        is_skin=is_skin,
+                    )
+                )
+
+        # 显示材质列表
+        has_non_skin = False
+        for mat_info in materials_info:
+            row = box.row()
+            if mat_info.is_skin:
+                row.label(text=f"[皮肤] {mat_info.name}", icon="CHECKMARK")
+            else:
+                row.label(text=f"[非皮肤] {mat_info.name}", icon="MESH_DATA")
+                has_non_skin = True
+            row.label(text=f"{mat_info.face_count} 面")
+
+        # 显示分离操作按钮
+        layout.separator()
+        col = layout.column()
+        col.enabled = has_non_skin
+        col.operator(
+            "vrm.separate_non_skin_faces",
+            text="分离非皮肤面",
+            icon="MESH_DATA",
+        )
+
+        if not has_non_skin:
+            layout.label(text="没有非皮肤材质可分离", icon="INFO")