Admin: tool registry, grouped nav, and an /admin/ hub

public/admin/testsheet.html

@@ -7,6 +7,8 @@
   .bar button { padding:9px 16px; border-radius:8px; border:0; cursor:pointer; font-weight:600; }
   .bar .go { background:linear-gradient(135deg,#51eaf1,#529eff); color:#04121a; }
   .bar .ghost { background:transparent; color:#e8ecff; border:1px solid rgba(255,255,255,.35); }
+  .bar .home { color:#8fb8ff; text-decoration:none; font-size:.85rem; margin-right:4px; }
+  .bar .home:hover { color:#51eaf1; }
   .note { padding:0 18px 14px; font-size:.85rem; line-height:1.6; opacity:.85; max-width:70rem; }
   .note code { background:rgba(255,255,255,.1); padding:1px 5px; border-radius:4px; }
   #status { font-size:.85rem; opacity:.9; }
@@ -27,6 +29,7 @@
 <body>
 
 <div class="bar">
+  <a class="home" href="/admin/">&larr; Admin</a>
   <button class="go" onclick="window.print()">Print A3</button>
   <button class="ghost" id="load">Load this layout onto the server</button>
   <span id="status"></span>