Unify nav across all pages; broaden safety section

- about, terms, enterprise_terms now all import and use shared nav()
- Any future nav change propagates everywhere automatically
- Remove Docs from nav (no docs yet)
- Safety: Hard Bell is for everyone, not just children - reframe copy,
  update cards and bottom callout to reflect universal applicability

src/enterprise_terms.el

@@ -2,6 +2,7 @@
 // Returns complete HTML using the shared page shell from styles.el.
 
 from styles import { page_open, page_close }
+from nav    import { nav }
 
 fn enterprise_terms_page() -> String {
     return page_open() + enterprise_terms_body() + page_close()
@@ -31,20 +32,7 @@ fn p_caps(text: String) -> String {
 }
 
 fn enterprise_terms_body() -> String {
-    return "
-<nav id=\"nav\">
-  <div class=\"nav-inner\">
-    <a href=\"/\" class=\"nav-logo\" aria-label=\"Neuron home\"><img src=\"/assets/brand/neuron-wordmark-on-light.png\" srcset=\"/assets/brand/neuron-wordmark-on-light@2x.png 2x\" alt=\"Neuron\" height=\"28\"></a>
-    <div class=\"nav-links\">
-      <a href=\"/#how-it-works\" class=\"nav-link\">How it works</a>
-      <a href=\"/#pricing\"       class=\"nav-link\">Pricing</a>
-      <a href=\"/#enterprise\"    class=\"nav-link\">Enterprise</a>
-      <a href=\"/about\"          class=\"nav-link\">About</a>
-      <a href=\"/#pricing\"       class=\"nav-cta\">Get Access</a>
-    </div>
-  </div>
-</nav>
-
+    return nav() + "
 <div style=\"max-width:720px;margin:0 auto;padding:6rem 2.5rem 8rem\">
   <div style=\"margin-bottom:3rem\">
     <a href=\"/\" style=\"font-family:var(--body);font-size:0.75rem;font-weight:500;letter-spacing:0.15em;text-transform:uppercase;color:var(--navy);text-decoration:none\">&#8592; Neuron</a>