fix(builder): item 15 — default header nav no longer links nonexistent pages

DEFAULT_HEADER_STATE's Navbar linked Home/About/Services/Contact, but a
brand new site only has a Home page — About/Services/Contact were dead
links on first click. Simplified the default to Home + an inert "Get
Started" CTA (href: '#') rather than seeding placeholder pages nobody
asked for. Updated default-header.test.ts's HTML-export assertions to
match the new default (and assert the removed links are gone).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

craft/src/state/PageContext.tsx

@@ -119,6 +119,13 @@ export function treeToCraftState(tree: SerializedTreeNode): string {
 // Container), so there was no menu to edit and the empty zone rendered as a
 // stray band above the page. Seeding a real Navbar gives every new site an
 // editable menu-with-links out of the box (and removes the empty-header gap).
+//
+// Item 15: the nav used to link Home/About/Services/Contact, but a brand
+// new site only has a "Home" page -- About/Services/Contact were dead links
+// on first click. Rather than seeding three empty placeholder pages nobody
+// asked for, the simpler default is a nav with just the one real page (Home)
+// plus a CTA button, which is inert (`href: '#'`) rather than pointing at a
+// page that doesn't exist. Users add pages/links as their site grows.
 // Node shape matches treeToCraftState() / Craft's actions.deserialize().
 export const DEFAULT_HEADER_STATE = JSON.stringify({
   ROOT: {
@@ -144,9 +151,7 @@ export const DEFAULT_HEADER_STATE = JSON.stringify({
       logoFontSize: '20px',
       links: [
         { text: 'Home', href: '/' },
-        { text: 'About', href: '#about' },
-        { text: 'Services', href: '#services' },
-        { text: 'Contact', href: '#contact', isCta: true },
+        { text: 'Get Started', href: '#', isCta: true },
       ],
       backgroundColor: '#ffffff',
       textColor: '#3f3f46',