fix(docs[spa]): Re-initialize prompt-copy buttons after SPA navigation

why: prompt-copy.js init ran once on DOMContentLoaded inside an IIFE.
After SPA navigation, new prompt blocks lacked markdown-preserving copy.
what:
- Expose init via window.__promptCopyInit in prompt-copy.js
- Call __promptCopyInit from reinit() in spa-nav.js

Author: tony

docs/_static/js/prompt-copy.js

@@ -53,6 +53,9 @@
     });
   }
 
+  // Expose init for SPA re-initialization (called by spa-nav.js reinit)
+  window.__promptCopyInit = init;
+
   if (document.readyState === "loading") {
     document.addEventListener("DOMContentLoaded", function () {
       setTimeout(init, 100);

docs/_static/js/spa-nav.js

@@ -155,6 +155,7 @@
   function reinit() {
     addCopyButtons();
     initScrollSpy();
+    if (typeof window.__promptCopyInit === "function") window.__promptCopyInit();
     var btn = document.querySelector(".content-icon-container .theme-toggle");
     if (btn) btn.addEventListener("click", cycleTheme);
   }