Navbar: showMobileMenu defaults to true for new Navbars and the seeded header

Existing Navbars (prop absent/false) are untouched: render default and toHtml stay falsy.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

craft/src/components/basic/Navbar.toHtml.test.ts

@@ -195,3 +195,13 @@ describe('Navbar.toHtml design tokens (#44)', () => {
     for (const hex of ['#3f3f46', '#e4e4e7']) expect(lower, `old ${hex}`).not.toContain(hex.toLowerCase());
   });
 });
+
+describe('Navbar mobile menu default', () => {
+  test('NEW Navbars (craft defaults) get the hamburger; a stored Navbar without the prop keeps its output', async () => {
+    const { Navbar } = await import('./Navbar');
+    expect((Navbar as any).craft.props.showMobileMenu).toBe(true);
+    const toHtml = (Navbar as any).toHtml;
+    expect(toHtml({}, '', 'n1').html).not.toContain('navbar-hamburger"');
+    expect(toHtml({ showMobileMenu: true }, '', 'n1').html).toContain('class="navbar-hamburger"');
+  });
+});

craft/src/components/basic/Navbar.tsx

@@ -246,7 +246,9 @@ Navbar.craft = {
     padding: '16px 24px',
     navAlignment: 'space-between',
     isSticky: false,
-    showMobileMenu: false,
+    // On for NEW Navbars (links overflow a phone otherwise). The component's render default and toHtml
+    // stay falsy so a stored Navbar that never had the prop keeps its exact output.
+    showMobileMenu: true,
     style: {
       borderBottom: `1px solid ${tokenRef('border')}`,
     },

craft/src/state/PageContext.tsx

@@ -252,7 +252,7 @@ export const DEFAULT_HEADER_STATE = JSON.stringify({
       padding: '16px 24px',
       navAlignment: 'space-between',
       isSticky: false,
-      showMobileMenu: false,
+      showMobileMenu: true,
       style: { borderBottom: '1px solid #e4e4e7' },
     },
     displayName: 'Navbar',