AGC生图工具说明补充角色与图集自动抠图语义

agc_generate_image 的 kind 说明补充：character 纯色底生成后自动抠图产出透明立绘且 prompt 只描述角色主体，art-spritesheet 自动抠图并切片，image 不做额外处理
taonier-art-assets Skill 的 Use 段同步同义英文说明
工具目录契约测试新增 kind 说明断言

apps/ai-game-creator-shell/src-tauri/resources/agc-skills/taonier-art-assets/SKILL.md

@@ -19,6 +19,12 @@ image, UI design image, or publication material; use `agc_edit_image` for an
 edit of an existing registered image; use `taonier_prepare_game_art` only for
 the complete game-art package and its canonical slices.
 
+With `agc_generate_image`, `kind="character"` and `kind="art-spritesheet"`
+generate the subject on a solid-colour background and automatically matte it
+away afterwards, producing transparent-background results; write the prompt
+for the subject only, never for a scene. `kind="image"` keeps the rendered
+frame without extra processing.
+
 When `agc_generate_image` is used with `kind="art-spritesheet"`, `sliceMode` is
 required and has no default, so decide it explicitly:
 

apps/ai-game-creator-shell/src-tauri/src/agent/direct_tools_mcp.rs

@@ -247,7 +247,7 @@ fn direct_tools_mcp_specs_for(controlled_web_search: bool, _cocos_editor_availab
                             "type": "string",
                             "enum": PLATFORM_ART_ASSET_GENERATION_KINDS,
                             "default": "image",
-                            "description": "image=普通新图，character=角色图，spec/icon-spec=统一视觉规范图（spec 是服务端同义词，客户端统一登记为 icon-spec），ui-prototype=完整 UI 设计图，art-spritesheet=透明游戏素材图集（项目须已有 icon-spec 规范图），publication-material=发布宣传图"
+                            "description": "image=普通新图（不做额外处理），character=角色图（纯色底生成后自动抠图，产出透明背景立绘，prompt 只描述角色主体），spec/icon-spec=统一视觉规范图（spec 是服务端同义词，客户端统一登记为 icon-spec），ui-prototype=完整 UI 设计图，art-spritesheet=透明游戏素材图集（纯色底生成后自动抠图并切片，项目须已有 icon-spec 规范图），publication-material=发布宣传图"
                         },
                         "aspectRatio": {
                             "type": "string",
@@ -2405,6 +2405,14 @@ mod tests {
         assert!(image_tool["description"]
             .as_str()
             .is_some_and(|description| description.contains("仅在用户明确要求生成新图时调用")));
+        assert!(
+            image_tool["inputSchema"]["properties"]["kind"]["description"]
+                .as_str()
+                .is_some_and(|description| description.contains("自动抠图")
+                    && description.contains("prompt 只描述角色主体")
+                    && description.contains("不做额外处理")),
+            "kind description must carry the auto-matting semantics"
+        );
         assert_eq!(
             image_tool["inputSchema"]["properties"]["sliceMode"]["enum"],
             json!(["connected-components", "grid"])