Fix iframe recursion and remove all localStorage/cookies site-wide

- Add target="_top" to all ← SPACE / back-to-root links so navigating
  back to index.html breaks out of the content iframe instead of loading
  it recursively inside itself (Images, Music, Watchlists hubs)
- Remove all localStorage usage: visited-star tracking in index.html
  (resets each visit, no persistence without storage), and lightbox
  "show once" guards in all section pages (lightboxes now show on every
  load — Videos, Watchlists, Music). build.py templates updated so
  future generated pages stay clean.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

index.html

@@ -762,7 +762,7 @@ body::after {
   var writingsLightboxShown   = false;
   var currentWritingIndex = 0;
   var writingElements     = [];
-  var visited          = JSON.parse(localStorage.getItem('sp-visited') || '{}');
+  var visited          = {};
   var starElements     = [];
   var srAnnounce       = document.getElementById('sr-announce');
   var backBtn          = document.getElementById('back-btn');
@@ -1154,14 +1154,12 @@ body::after {
     // Writings star activates the writings sub-map instead of rising a frame
     if (star.id === 'writings') {
       visited[star.id] = true;
-      localStorage.setItem('sp-visited', JSON.stringify(visited));
       starElements[index].classList.add('visited');
       selectWritingsSection();
       return;
     }
 
     visited[star.id] = true;
-    localStorage.setItem('sp-visited', JSON.stringify(visited));
     starElements[index].classList.add('visited');
     starElements.forEach(function (el) { el.classList.remove('current'); });
     starElements[index].classList.add('current');