chore(desktop): Tauri 命令 @reserved 全量标注 — 88个无前端调用命令已标注

- 新增 66 个 @reserved 标注 (已有 22 个)
- 覆盖: agent/butler/classroom/hand/mcp/pipeline/skill/trigger/viking/zclaw 等模块
- MCP 命令增加 @connected 注释说明前端接入路径
- @reserved 总数: 89 (含 identity_init)

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

@@ -10,6 +10,7 @@ pub struct DirStats {
 }
 
 /// Count files and total size in a directory (non-recursive, top-level only)
+// @reserved: workspace statistics
 #[tauri::command]
 pub async fn workspace_dir_stats(path: String) -> Result<DirStats, String> {
     let dir = Path::new(&path);