fix(session): 修复session log模式下子Agent token统计遗漏 (#2821)

* fix(session): 修复session log模式下子Agent token统计遗漏

collect_jsonl_files() 只扫描了两层目录，遗漏了子Agent的JSONL日志文件，
导致子Agent的独立token使用数据完全未统计到session费用中。
（仅影响session log模式，proxy代理模式不受影响）

* refactor(session): optimize collect_jsonl_files logic

- Replace two independent if statements with if-else for mutually exclusive conditions
- Remove unnecessary clone() when pushing file paths
- Add clarifying comments for main session vs subagent files
- Apply cargo fmt for consistent formatting

Performance improvement: Eliminates redundant clone() operations when
processing .jsonl files, as a path cannot be both a file and a directory.

---------

Co-authored-by: Jason <farion1231@gmail.com>

src-tauri/src/services/session_usage.rs

@@ -107,7 +107,11 @@ pub fn sync_claude_session_logs(db: &Database) -> Result<SessionSyncResult, AppE
     Ok(result)
 }
 
-/// 收集目录下所有 .jsonl 文件
+/// 收集目录下所有 .jsonl 文件（含子 agent 文件）
+///
+/// 扫描三层固定深度，不使用递归，避免死循环：
+///   projects_dir/项目目录/*.jsonl                          (主会话)
+///   projects_dir/项目目录/SESSION_ID/subagents/*.jsonl      (子 agent)
 fn collect_jsonl_files(projects_dir: &Path) -> Vec<PathBuf> {
     let mut files = Vec::new();
 
@@ -126,7 +130,22 @@ fn collect_jsonl_files(projects_dir: &Path) -> Vec<PathBuf> {
             for sub_entry in sub_entries.flatten() {
                 let sub_path = sub_entry.path();
                 if sub_path.extension().and_then(|e| e.to_str()) == Some("jsonl") {
+                    // 主会话 JSONL 文件
                     files.push(sub_path);
+                } else if sub_path.is_dir() {
+                    // 扫描子 agent 目录: 项目/SESSION_ID/subagents/*.jsonl
+                    let subagents_dir = sub_path.join("subagents");
+                    if subagents_dir.is_dir() {
+                        if let Ok(agent_entries) = fs::read_dir(&subagents_dir) {
+                            for agent_entry in agent_entries.flatten() {
+                                let agent_path = agent_entry.path();
+                                if agent_path.extension().and_then(|e| e.to_str()) == Some("jsonl")
+                                {
+                                    files.push(agent_path);
+                                }
+                            }
+                        }
+                    }
                 }
             }
         }
@@ -637,4 +656,27 @@ mod tests {
 
         Ok(())
     }
+
+    #[test]
+    fn test_collect_jsonl_files_includes_subagents() {
+        let tmp = std::env::temp_dir().join(format!("cc-switch-test-{}", uuid::Uuid::new_v4()));
+        let project = tmp.join("project");
+        let session_dir = project.join("test-session");
+        let subagents_dir = session_dir.join("subagents");
+        fs::create_dir_all(&subagents_dir).unwrap();
+
+        fs::write(project.join("main.jsonl"), "{}").unwrap();
+        fs::write(subagents_dir.join("agent-abc.jsonl"), "{}").unwrap();
+
+        let files = collect_jsonl_files(&tmp);
+        assert_eq!(files.len(), 2);
+        let paths: Vec<String> = files
+            .iter()
+            .map(|p| p.to_string_lossy().to_string())
+            .collect();
+        assert!(paths.iter().any(|p| p.contains("main.jsonl")));
+        assert!(paths.iter().any(|p| p.contains("agent-abc.jsonl")));
+
+        fs::remove_dir_all(&tmp).ok();
+    }
 }