feat(comments): full 1:1 zibll comment kernel for posts, forum, shop

Extract shared comment helpers (content/item/form/geo/actions), port GIF
[g=] smilies + FixedInput/moveForm UX, wire close_comments/city/quick
settings, REST comment get, and align product review chrome with zibll.

assets/js/core/comment-fixed-input.js

@@ -0,0 +1,90 @@
+/**
+ * Mobile FixedInput + autoheight for comment respond (zibll parity).
+ */
+(function () {
+  'use strict';
+
+  function $(sel, root) {
+    return (root || document).querySelector(sel);
+  }
+
+  function FixedInput(el, action) {
+    if (!el) return;
+    if (!el.dataset.fixedBound) {
+      el.addEventListener('click', function (e) {
+        if (e.target && e.target.closest && e.target.closest('.fixed-body')) {
+          FixedInput(el, 'hide');
+        }
+      });
+      el.dataset.fixedBound = '1';
+    }
+    if (action === 'show') {
+      el.classList.add('show');
+      window.setTimeout(function () {
+        var field = el.querySelector('textarea, input');
+        if (field) field.focus();
+      }, 100);
+      return;
+    }
+    if (action === 'hide') {
+      var cancel = el.querySelector('#cancel-comment-reply-link');
+      if (cancel) cancel.click();
+      el.querySelectorAll('input,textarea').forEach(function (n) {
+        try { n.blur(); } catch (e) {}
+      });
+      el.querySelectorAll('.dropup.open, .open').forEach(function (n) {
+        n.classList.remove('open');
+      });
+      el.classList.remove('show');
+    }
+  }
+
+  document.addEventListener('click', function (e) {
+    var trigger = e.target && e.target.closest ? e.target.closest('[fixed-input]') : null;
+    if (!trigger) return;
+    e.preventDefault();
+    var targetSel = trigger.getAttribute('fixed-input') || '#respond';
+    var panel = document.querySelector(targetSel);
+    var comments = document.getElementById('comments');
+    if (comments && comments.scrollIntoView) {
+      comments.scrollIntoView({ behavior: 'smooth', block: 'start' });
+    }
+    FixedInput(panel, 'show');
+  });
+
+  // Autoheight textareas.
+  function bindAutoheight(ta) {
+    if (!ta || ta.dataset.autoheightBound) return;
+    ta.dataset.autoheightBound = '1';
+    var max = parseInt(ta.getAttribute('maxheight') || '188', 10) || 188;
+    var resize = function () {
+      ta.style.height = 'auto';
+      var h = Math.min(ta.scrollHeight, max);
+      ta.style.height = h + 'px';
+      ta.style.overflowY = ta.scrollHeight > max ? 'auto' : 'hidden';
+    };
+    ta.addEventListener('input', resize);
+    resize();
+  }
+
+  function scan() {
+    document.querySelectorAll('textarea[autoheight], textarea.grin').forEach(bindAutoheight);
+  }
+
+  document.addEventListener('DOMContentLoaded', scan);
+  if (window.AksrtFrontend && typeof window.AksrtFrontend.register === 'function') {
+    window.AksrtFrontend.register('aksrt-comment-fixed-input', function (root) {
+      scan();
+      // Expose for submit hide.
+      root = root || document;
+      var respond = root.querySelector ? root.querySelector('#respond') : document.getElementById('respond');
+      if (respond) {
+        respond.aksrtFixedInput = function (action) {
+          FixedInput(respond, action);
+        };
+      }
+    });
+  }
+
+  window.AksrtFixedInput = FixedInput;
+})();