clearPersistedSession

Removes the locally persisted token.

No server-side revoke endpoint exists, so this does not affect a Portal already holding the credential; it prevents a future restoreSession from returning it.

Can be used when recovering from corrupt storage, or clearing a leftover before a fresh sign-in without having a Portal instance

Also forgets the grant handleRedirect last exchanged, so a redirect re-delivered after a sign-out cannot replay the session that was just cleared.

Throws