feat(usable): package gui-host validation snapshot

Co-Authored-By: Paperclip <noreply@paperclip.ing>

TUI_BACKEND_CONTRACT.md

@@ -195,16 +195,25 @@ JSON 返回 envelope：
 {
   "status": "success",
   "operation": "query",
+  "state": "success",
   "data": {}
 }
 ```
 
+- `status` 继续只区分 envelope 级成功/失败
+- `state` 对齐共享应用层状态：
+  - `connect`：`success`
+  - `inspect`：`success | empty`
+  - `query`：`success | empty`
+  - `export`：`success`
+
 错误返回 envelope：
 
 ```json
 {
   "status": "error",
   "operation": "query",
+  "state": "error",
   "error": {
     "operation": "query",
     "kind": "query",