feat: 导入的 skills 默认存到 ~/.ias/skills/

- Import/Delete 目标改为 ~/.ias/skills/（全局共享）
- SkillRegistry::load() 返回 (Self, Vec<String>) 替代 Result
  允许部分加载：格式不兼容的 skill 记录警告但不阻止加载
- 新增 global_skills_dir() 辅助函数

src/tools/parser.rs

@@ -210,32 +210,27 @@ mod tests {
     #[test]
     fn test_load_all_system_skills() {
         let rt = tokio::runtime::Runtime::new().unwrap();
-        let result = rt.block_on(crate::tools::registry::SkillRegistry::load(
+        let (registry, errors) = rt.block_on(crate::tools::registry::SkillRegistry::load(
             "resources/skills",
             "/nonexistent",
         ));
-        match result {
-            Ok(registry) => {
-                assert_eq!(registry.count(), 9, "应该有 9 个系统技能");
-                let names: Vec<&str> = registry.list_specs().iter().map(|s| s.name.as_str()).collect();
-                println!("已加载技能: {:?}", names);
-                assert!(names.contains(&"manage_memos"));
-                assert!(names.contains(&"manage_skill"));
-                assert!(names.contains(&"get_current_datetime"));
-                assert!(names.contains(&"query_weather"));
-                assert!(names.contains(&"search_web"));
-                assert!(names.contains(&"email"));
-                assert!(names.contains(&"execute_shell"));
-                assert!(names.contains(&"list_scheduled_tasks"));
-                assert!(names.contains(&"manage_scheduled_task"));
-            }
-            Err(errors) => {
-                for e in &errors {
-                    eprintln!("加载失败: {}", e);
-                }
-                panic!("技能加载失败");
+        if !errors.is_empty() {
+            for e in &errors {
+                eprintln!("加载警告: {}", e);
             }
         }
+        assert_eq!(registry.count(), 9, "应该有 9 个系统技能");
+        let names: Vec<&str> = registry.list_specs().iter().map(|s| s.name.as_str()).collect();
+        println!("已加载技能: {:?}", names);
+        assert!(names.contains(&"manage_memos"));
+        assert!(names.contains(&"manage_skill"));
+        assert!(names.contains(&"get_current_datetime"));
+        assert!(names.contains(&"query_weather"));
+        assert!(names.contains(&"search_web"));
+        assert!(names.contains(&"email"));
+        assert!(names.contains(&"execute_shell"));
+        assert!(names.contains(&"list_scheduled_tasks"));
+        assert!(names.contains(&"manage_scheduled_task"));
     }
 
     #[test]