feat: unified preview eye icon component, enhanced search & preview

- Unify filter group and filter value preview icons into shared
  .filter-chip-wrapper + .chip-preview-btn component pattern
- Remove old .toggle-count.clickable inline eye icon approach
- Add dropdown-level event handler for preview buttons (dropdown
  appended to body, needs separate delegation)
- Enhanced EntitySearchEngine with improved product condition
  resolution and preview data
- Add EntityPreviewHandler for richer preview popovers
- Various SCSS improvements for chips, groups, and list-preview

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

sources/scss/components/_entity-selector.scss

@@ -368,6 +368,7 @@
 // Single mode specific styles
 .target-conditions-trait.single-mode,
 .entity-selector-trait.single-mode {
+    // Hide tabs in standalone layout (has separate header, 1 tab is redundant)
     .target-block-tabs {
         display: none;
     }
@@ -375,6 +376,11 @@
     .target-block-container {
         display: block;
     }
+
+    // In form-content layout, always show tabs — they serve as the block title
+    .entity-selector-tabs-row .target-block-tabs {
+        display: flex;
+    }
 }
 
 // Header action buttons