Conditionally move the primary nav into the header, if no header right widget area is active.

functions.php

<?php

add_action( 'genesis_before_header', 'leaven_maybe_move_primary_nav' );
/**
 * Maybe move the primary navigation to the header (if no widget in header-right).
 */
function leaven_maybe_move_primary_nav() {
	if ( is_active_sidebar( 'header-right' ) ) {
		return;
	}
	remove_action( 'genesis_after_header', 'genesis_do_nav' );
	add_action( 'genesis_header', 'genesis_do_nav', 11 );
}

style.css

/* ## Full Width Header
----------------------------------------- */
.header-full-width .title-area {
	-webkit-box-flex: 1;
	-webkit-flex-grow: 1;
	-ms-flex-positive: 1;
	flex-grow: 1;
}

.header-full-width .nav-primary {
	background-color: transparent;
	-webkit-box-flex: 1;
	-webkit-flex-grow: 1;
	-ms-flex-positive: 1;
	flex-grow: 1;
	max-height: 76px;
	z-index: 100;
}

.header-full-width .nav-primary .menu-item:last-of-type > a {
	padding-right: 0;
}

.header-full-width .nav-primary .genesis-nav-menu {
	text-align: right;
}

.header-full-width .nav-primary .genesis-nav-menu .menu-item:hover .sub-menu .sub-menu {
	margin: -55px 0;
	left: -199px;
}

.header-full-width .site-header {
  background-color: #292929;
	background-color: rgba(41, 41, 41, 0.9);
	width: 100%;
	z-index: 800;
}

.header-full-width .site-header > .wrap {
	display: -webkit-box;
	display: -webkit-flex;
	display: -ms-flexbox;
	display: flex;
	-webkit-box-pack: justify;
	-webkit-justify-content: space-between;
	-ms-flex-pack: justify;
	justify-content: space-between;
	padding: 0;
}

.header-full-width .site-title a,
.header-full-width .site-title a:hover,
.header-full-width .site-description {
	color: #fff;
}

.header-full-width.header-image .title-area {
	padding: 0;
}

/* ## Widget Area
--------------------------------------------- */
.site-header .widget-area {
	-webkit-box-ordinal-group: 4;
	-webkit-order: 3;
	-ms-flex-order: 3;
	order: 3;
	width: 100%;
}