fix: add missing cancelAbstractPreview function and related state

The openImportWindow and closeImportWindow functions referenced
cancelAbstractPreview which was not defined. Added:
- hoverTimerId, hoveredItemKey, previewItemKey to state
- previewPopover to elements object
- cancelAbstractPreview function

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

src/zotero_kb/templates/index.html

@@ -492,6 +492,9 @@
         loadingCollectionKey: null,
         nextCollectionItemsRequestToken: 0,
         activeCollectionItemsRequestToken: 0,
+        hoveredItemKey: null,
+        hoverTimerId: null,
+        previewItemKey: null,
       };
 
       const elements = {
@@ -514,6 +517,7 @@
         windowCollectionStatus: document.getElementById("window-collection-status"),
         windowCollectionTree: document.getElementById("window-collection-tree"),
         windowCollectionItems: document.getElementById("window-collection-items"),
+        previewPopover: document.getElementById("item-preview-popover"),
         currentProjectLabel: document.getElementById("current-project-label"),
         cardList: document.getElementById("card-list"),
         cardDetail: document.getElementById("card-detail"),
@@ -667,6 +671,20 @@
         persistWindowSessionState();
       }
 
+      function cancelAbstractPreview() {
+        if (state.hoverTimerId !== null) {
+          window.clearTimeout(state.hoverTimerId);
+          state.hoverTimerId = null;
+        }
+        state.hoveredItemKey = null;
+        state.previewItemKey = null;
+        elements.previewPopover.hidden = true;
+        elements.previewPopover.setAttribute("aria-hidden", "true");
+        elements.previewPopover.textContent = "";
+        elements.previewPopover.style.top = "";
+        elements.previewPopover.style.left = "";
+      }
+
       function setStatus(target, message, isError = false) {
         target.textContent = message || "";
         target.classList.toggle("error", Boolean(isError));