fix(desktop): 功能验证 6 项缺陷修复

- ISS-002: SkillInfoResponse 增加 source/path 字段，修复技能系统显示 0 个
- ISS-003: Sidebar 添加自动化/技能市场导航入口 + App 返回按钮
- ISS-004: SaaS fetchAvailableModels 添加 .catch() 防限流崩溃
- ISS-006: SaaSSettings/PricingPage 包裹 ErrorBoundary 防白屏
- ISS-008: listModels 加载 localStorage 自定义模型，修复仅显示 1 个模型
- configStore listSkills 映射添加 source/path 转发

desktop/src-tauri/src/kernel_commands/skill.rs

@@ -30,6 +30,14 @@ pub struct SkillInfoResponse {
     pub enabled: bool,
     pub triggers: Vec<String>,
     pub category: Option<String>,
+    #[serde(default = "default_source")]
+    pub source: String,
+    #[serde(default)]
+    pub path: Option<String>,
+}
+
+fn default_source() -> String {
+    "builtin".to_string()
 }
 
 impl From<zclaw_skills::SkillManifest> for SkillInfoResponse {
@@ -45,6 +53,8 @@ impl From<zclaw_skills::SkillManifest> for SkillInfoResponse {
             enabled: manifest.enabled,
             triggers: manifest.triggers,
             category: manifest.category,
+            source: "builtin".to_string(),
+            path: None,
         }
     }
 }