Implement catalog startup diagnostics (T-616)

app-win7/ui/gio/shell_catalog.go

@@ -270,6 +270,20 @@ func (shell *AppShell) layoutEmptyState(
 		if shell.model.TotalCount() == 0 {
 			title = "软件目录尚未加载"
 			body = "联网刷新或读取已验证缓存后会显示软件。"
+			switch shell.catalogState {
+			case catalogStateLoading:
+				title = "正在加载软件目录"
+				body = "正在等待已验证 Catalog 快照。"
+			case catalogStateUnconfigured:
+				title = "Catalog 来源尚未配置"
+				body = "此构建未装配可信发布配置，因此未显示任何软件。"
+			case catalogStateLoadFailed:
+				title = "Catalog 加载失败"
+				body = "未收到可验证的 Catalog；已显示的目录不会被清除。"
+			case catalogStateReady:
+				title = "Catalog 暂无可显示软件"
+				body = "已验证 Catalog 没有适用于当前目标的软件。"
+			}
 		}
 		return layout.Flex{Axis: layout.Vertical, Alignment: layout.Middle}.Layout(
 			gtx,