[FEATURE] Add "Claude Platform for AWS" / awsAuthRefresh entry to /login Third-party menu

Context

Claude Code supports awsAuthRefresh in ~/.claude/settings.json for Claude Platform for AWS users — a shell command (e.g. okta-aws-cli web) that refreshes AWS STS credentials via an organization's configured OIDC flow.

Today the /login Third-party submenu has entries for Bedrock and other third-party providers, but no entry for Claude Platform for AWS / awsAuthRefresh.

Request

Add a /login Third-party menu item — e.g. "Claude Platform for AWS (refresh credentials)" — that executes the awsAuthRefresh command configured in settings. Disabled or hidden when awsAuthRefresh is not set.

Why

Closes the loop on the companion bug #67529: when AWS STS tokens expire mid-session and Claude Code surfaces Please run /login, the user could actually run /login, choose the menu entry, and re-authenticate without exiting the session.

Related

Companion bug: #67529