Add [sso].public_url: the browser-facing MCIAS base URL for the SSO
authorize redirect, kept separate from [mcias].server_url (the internal
address used for the server-to-server code exchange). Enables public SSO
without routing internal auth through the edge. Bumps mcdsl to v1.9.0.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>