[client] Force interactive login when extending the auth session

A session extend must be answered from the account the peer is registered
under. With a silent PKCE flow (DisablePromptLogin or max_age=0) the IdP
answers from whatever session it already holds, which need not be the
peer's account when several are signed in; the token then fails the
user match in ExtendAuthSession with no way to pick another account.

Mark the PKCE flow request as a session extend so the management server
can force prompt=login for it, overriding the configured silent flow.

client/cmd/login.go

@@ -408,7 +408,7 @@ func foregroundGetTokenInfo(ctx context.Context, cmd *cobra.Command, config *pro
 		hint = profileState.Email
 	}
 
-	oAuthFlow, err := auth.NewOAuthFlow(ctx, config, util.HasGraphicalSession(), false, hint)
+	oAuthFlow, err := auth.NewOAuthFlow(ctx, config, util.HasGraphicalSession(), false, hint, false)
 	if err != nil {
 		return nil, err
 	}