Merge 'fix/readme-sso-start-url-userportal' into 'master'

docs(readme): clarify SSO start-url format with /userportal examples

See merge request: !62

Author: bytestarter

README.EN.MD

@@ -169,7 +169,7 @@ This command creates or updates an SSO session for later use with `configure sso
 
 ```shell
 name: SSO session name; if omitted, enter interactive selection/creation mode
-start-url: SSO Start URL; required; if editing an existing session, Enter keeps the default
+start-url: SSO Start URL; required. Format: your sign-in URL with the `/userportal` suffix, for example `https://{custom}.volccloudidentity.com/userportal`. If editing an existing session, press Enter to keep the default
 region: SSO region; required; default is cn-beijing, existing session values are used as defaults
 registration-scopes: SSO scope list (comma-separated); allowed values are cloudidentity:account:access, offline_access
 ```

README.MD

@@ -175,7 +175,7 @@ ve configure sso-session --name [会话名] --start-url [SSO Start URL] --region
 
 ```shell
 name: SSO 会话名称；未提供时进入交互式选择/创建模式
-start-url: SSO Start URL；必填，若已有会话则支持回车使用默认值
+start-url: SSO Start URL；必填。格式为“用户登录链接 + /userportal”后缀，例如 `https://{custom}.volccloudidentity.com/userportal`；若编辑已有会话，回车可沿用默认值
 region: SSO 区域；必填，默认 cn-beijing，已有会话会回填默认值
 registration-scopes: SSO scope 列表（逗号分隔）；允许值仅 cloudidentity:account:access, offline_access
 ```