Drop turtle, honor ?template= URL param, add warp easter egg

- Removed the cosmos turtle (CSS rules + auto-load probe + JS hook).
  Reduced-motion turtle branch removed too.
- ?template=editorial|swiss|cosmos URL param now wins over the value
  in data/links.json (and the cached localStorage fallback). Wired in
  both the pre-paint boot script and main() so deep links work
  without flashing the wrong template.
- New hidden easter egg: type the letters w-a-r-p anywhere on the
  page (no input focused) and the page reloads on the next template
  in the cycle editorial -> swiss -> cosmos -> editorial. The URL is
  updated with the new ?template= param so the override survives
  refresh and is shareable. A small "↯ <name>" toast pops up after
  the reload via sessionStorage handoff, fades after ~2.5s, respects
  prefers-reduced-motion.
- README documents both the URL param and the warp keyword.

index.html

@@ -22,12 +22,19 @@
   <link href="https://fonts.googleapis.com/css2?family=Archivo:wght@400;500;600;700;900&family=DM+Serif+Display:ital@0;1&family=Fraunces:opsz,wght,SOFT,WONK@9..144,300..600,30..100,0..1&family=Geist:wght@300;400;500;600&family=Geist+Mono:wght@400;500&family=Orbitron:wght@400;500;700;900&display=swap" rel="stylesheet">
 
   <script>
-    // Apply saved theme + template before paint to avoid flash
+    // Apply saved theme + template before paint to avoid flash.
+    // URL ?template=… wins over the cached value so deep links work.
     try {
       var t = localStorage.getItem("dlstack-theme");
       if (t === "light" || t === "dark") document.documentElement.dataset.theme = t;
-      var tpl = localStorage.getItem("dlstack-template");
-      if (tpl === "swiss" || tpl === "editorial" || tpl === "cosmos") document.documentElement.dataset.template = tpl;
+      var qtpl = null;
+      try { qtpl = new URL(location.href).searchParams.get("template"); } catch (e) {}
+      if (qtpl === "swiss" || qtpl === "editorial" || qtpl === "cosmos") {
+        document.documentElement.dataset.template = qtpl;
+      } else {
+        var tpl = localStorage.getItem("dlstack-template");
+        if (tpl === "swiss" || tpl === "editorial" || tpl === "cosmos") document.documentElement.dataset.template = tpl;
+      }
     } catch (e) {}
   </script>