refactor(post-content): remove lightbox/lazy-load, keep copy only

the lightbox + IntersectionObserver lazy-load now live in lightbox.js;
post-content.js is reduced to just the code-block copy button.

public/js/post-content.js

@@ -40,101 +40,9 @@
     }
   }
 
-  function closeLightbox(overlay) {
-    if (overlay && overlay.parentNode) {
-      overlay.parentNode.removeChild(overlay);
-      document.body.style.overflow = "";
-    }
-  }
-
-  function initImageZoom(root) {
-    var containers = root.querySelectorAll(".blur-img");
-    for (var i = 0; i < containers.length; i++) {
-      var container = containers[i];
-      if (container.getAttribute("data-blur-init")) continue;
-      container.setAttribute("data-blur-init", "true");
-
-      var fullImg = container.querySelector(".blur-img-full");
-      if (!fullImg) continue;
-      var fullSrc = fullImg.getAttribute("data-src");
-      if (!fullSrc) continue;
-
-      // 加载高清图：onload 后加 is-loaded 触发 CSS opacity 淡入
-      fullImg.addEventListener("load", function () {
-        this.classList.add("is-loaded");
-      });
-
-      // 懒加载：进入视口才设 src
-      if ("IntersectionObserver" in window) {
-        var io = new IntersectionObserver(
-          function (entries) {
-            entries.forEach(function (entry) {
-              if (entry.isIntersecting) {
-                fullImg.src = fullSrc;
-                io.unobserve(container);
-              }
-            });
-          },
-          { rootMargin: "200px" }
-        );
-        io.observe(container);
-      } else {
-        // 不支持 IO：直接加载
-        fullImg.src = fullSrc;
-      }
-
-      // 灯箱：点击用高清图 URL 放大
-      (function (src, altText) {
-        container.addEventListener("click", function (e) {
-          e.preventDefault();
-          var overlay = document.createElement("div");
-          overlay.className = "md-image-lightbox-overlay";
-
-          var containerEl = document.createElement("div");
-          containerEl.className = "md-image-lightbox-content";
-
-          var bigImg = document.createElement("img");
-          bigImg.src = src;
-          bigImg.alt = altText;
-
-          var closeBtn = document.createElement("button");
-          closeBtn.className = "md-image-lightbox-close";
-          closeBtn.textContent = "\u2715";
-
-          containerEl.appendChild(bigImg);
-          containerEl.appendChild(closeBtn);
-          overlay.appendChild(containerEl);
-          document.body.appendChild(overlay);
-          document.body.style.overflow = "hidden";
-
-          var onKey = function (ev) {
-            if (ev.key === "Escape") {
-              cleanup(overlay, onKey);
-            }
-          };
-          var cleanup = function (ol, kh) {
-            closeLightbox(ol);
-            document.removeEventListener("keydown", kh);
-          };
-          overlay.addEventListener("click", function () {
-            cleanup(overlay, onKey);
-          });
-          containerEl.addEventListener("click", function (ev) {
-            ev.stopPropagation();
-          });
-          closeBtn.addEventListener("click", function () {
-            cleanup(overlay, onKey);
-          });
-          document.addEventListener("keydown", onKey);
-        });
-      })(fullSrc, fullImg.getAttribute("alt") || "");
-    }
-  }
-
   window.__initPostContent = function (selector) {
     var root = document.querySelector(selector);
     if (!root) return;
     initCopyButtons(root);
-    initImageZoom(root);
   };
 })();