refactor: 大文件模块化拆分、自进化Skill管线、前端设计系统统一

后端：
  - runtime: 拆分 AgentConfig/events/duplicate_detector 为独立模块
  - error_recovery: 1499行单体拆为 classification(21种FailoverReason)/overflow/mod
  - executor: 提取 helpers.rs (PreparedCall/ToolExecutionResult/execute_single_tool)
  - skills: 新增 SkillCreator + SelfImprovePipeline（模式检测→自动生成SKILL.md→质量审查）
  - clients/llm: 拆分为 chat/embedding/types 三个子模块
  - services/download: 1548行拆为 mod/headers(反爬+SSRF)/strategies(多级回退)
  - services/batch/asset: 1264行拆为 mod/helpers/process

  前端：
  - 设计系统统一: sky/indigo → blueprint 色系, rounded-xl→lg, shadow-lg→sm
  - 删除 Vite 模板残留 App.css
  - GlobalDialog/PaperDetailModal/UncachedPaperModal 提取公共 BaseModal 组件

src/agent/runtime/duplicate_detector.rs

@@ -0,0 +1,27 @@
+// src/agent/runtime/duplicate_detector.rs
+//
+// 同质调用检测器：检测连续重复的工具调用，防止死循环。
+
+/// 同质调用检测器
+#[derive(Debug, Default)]
+pub struct DuplicateDetector {
+    last_call: Option<(String, String)>, // (tool_name, arguments)
+    consecutive_count: usize,
+}
+
+impl DuplicateDetector {
+    /// 记录一次调用，返回是否检测到死循环
+    pub fn record(&mut self, tool_name: &str, arguments: &str, threshold: usize) -> bool {
+        let key = (tool_name.to_string(), arguments.to_string());
+        if self.last_call.as_ref() == Some(&key) {
+            self.consecutive_count += 1;
+            if self.consecutive_count >= threshold {
+                return true;
+            }
+        } else {
+            self.last_call = Some(key);
+            self.consecutive_count = 1;
+        }
+        false
+    }
+}