Restore Approach section; remove Foundation from site; unify navbar

- Revert the accidental Approach-section removal (restore homepage Approach)
- Remove the Foundation page for now (recoverable via git history; Typst
  sources retained in houston-labs-foundation/)
- Standardize the navbar across all pages: Focus / Approach / Resources /
  Contact / Email us, brand links home

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

index.html

@@ -29,7 +29,7 @@
   <!-- NAV -->
   <header class="nav-wrap">
     <nav class="nav">
-      <a class="brand" href="#top">
+      <a class="brand" href="/">
         <span class="brand-badge">
           <svg viewBox="0 0 32 32" width="20" height="20" aria-hidden="true">
             <defs><linearGradient id="m1" x1="0" y1="0" x2="0" y2="1"><stop offset="0" stop-color="#fff"/><stop offset=".5" stop-color="#9aa1b0"/><stop offset="1" stop-color="#eef1f6"/></linearGradient></defs>
@@ -39,10 +39,10 @@
         <span class="brand-name">HOUSTON&nbsp;LABS</span>
       </a>
       <div class="nav-links">
-        <a href="#focus">Focus</a>
-        <a href="foundation/">Foundation</a>
-        <a href="resources/">Resources</a>
-        <a href="#contact">Contact</a>
+        <a href="/#focus">Focus</a>
+        <a href="/foundation/">Foundation</a>
+        <a href="/resources/">Resources</a>
+        <a href="/#contact">Contact</a>
         <a class="nav-pill" href="mailto:contact@houstonlabs.us">Email&nbsp;us</a>
       </div>
     </nav>