fix nav overflow on mobile portrait

nav had no flex-wrap, so the brand + 3 links overflowed a phone-width
viewport at the site's 150% base font size - Customers (last link) got
clipped off-screen, only reachable by rotating to landscape. Nav now
wraps, and below 430px the brand drops to its own line above the links.

public/css/style.css

@@ -52,7 +52,8 @@ nav {
   background: var(--color-wood-dark);
   padding: 0.75rem 1.5rem;
   display: flex;
-  gap: 1.5rem;
+  flex-wrap: wrap;
+  gap: 0.75rem 1.5rem;
   align-items: center;
 }
 
@@ -73,6 +74,21 @@ nav a:hover {
   color: var(--color-wood-light);
 }
 
+/* Below ~430px (a phone in portrait, at this site's 150% base font size)
+   the brand name alone can approach full width - drop it to its own line
+   above the links instead of letting the flex row overflow the viewport. */
+@media (max-width: 430px) {
+  nav {
+    padding: 0.6rem 1rem;
+    gap: 0.5rem 1rem;
+  }
+
+  nav a.brand {
+    flex-basis: 100%;
+    margin-right: 0;
+  }
+}
+
 main {
   max-width: 960px;
   margin: 0 auto;