fix(sidebar): restore database-first sticky headers

apps/desktop/src/components/sidebar/ConnectionTree.vue

@@ -785,15 +785,14 @@ function readExpandedSidebarSchemas(): Array<{ id: string; label: string }> {
   return expanded;
 }
 
-// The plain (non-virtualized) renderer keeps the sticky database/schema header
-// via native CSS position: sticky on the container rows, mirroring the overlay
-// the virtual branch renders. Only container rows stick; children scroll under
-// them until the next container takes over.
-function isPlainStickyContainerNode(node: TreeNode): boolean {
+// The plain (non-virtualized) renderer uses the same container selection as the
+// virtual sticky overlay: database containers take precedence, while schema
+// containers stick only in trees without a database-level container.
+function isPlainStickyContainerNode(index: number): boolean {
   // Mirror the virtual branch's sticky overlay: both suppress sticky headers
   // while a search filter is active so filtered rows don't pin at the top.
   if (isTreeSearchFiltering.value) return false;
-  return DATABASE_LEVEL_TYPES.has(node.type) || SCHEMA_LEVEL_TYPES.has(node.type);
+  return flatTreeIndex.value.stickyContainerIndexByIndex[index] === index;
 }
 
 const sidebarLayoutMonitor = createSidebarLayoutMonitor({
@@ -2506,7 +2505,7 @@ defineExpose({ focusSearch, createNewGroup, collapseAllTreeNodes, locateTabInSid
             />
           </template>
         </RecycleScroller>
-        <div v-if="stickyNode" class="sticky-database-header pointer-events-auto absolute inset-x-0 top-0 z-[5] border-b border-border/60" :style="stickyHeaderStyle">
+        <div v-if="stickyNode" class="sticky-database-header pointer-events-auto absolute inset-x-0 top-0 z-[5]" :style="stickyHeaderStyle">
           <TreeItem
             :node="stickyNode.node"
             :depth="stickyNode.depth"
@@ -2539,7 +2538,7 @@ defineExpose({ focusSearch, createNewGroup, collapseAllTreeNodes, locateTabInSid
         <div ref="plainTreeScrollerRef" class="sidebar-tree connection-tree-scroller h-full overflow-y-auto" :class="sidebarTreeOverflowClass" :style="sidebarTreeScrollerStyle" @click="clearSidebarSelection" @scroll.passive="onTreeScroll">
           <div class="connection-tree-content">
             <TreeItem
-              v-for="item in flatNodes"
+              v-for="(item, index) in flatNodes"
               :key="item.renderKey"
               :node="item.node"
               :depth="item.depth"
@@ -2548,7 +2547,7 @@ defineExpose({ focusSearch, createNewGroup, collapseAllTreeNodes, locateTabInSid
               :pending-rename="pendingRenameNodeId === item.node.id"
               :highlighted="highlightedNodeId === item.id"
               :comment-label-width="sidebarCommentLabelWidths.get(item.node.id)"
-              :sticky-header="isPlainStickyContainerNode(item.node)"
+              :sticky-header="isPlainStickyContainerNode(index)"
               @context-menu="(event, node) => openSidebarContextMenu(event, node, contextMenuSlot.onContextMenu)"
               @rename-started="pendingRenameNodeId = null"
               @group-created="startRenamingCreatedGroup"

apps/desktop/src/components/sidebar/TreeItem.vue

@@ -1380,7 +1380,7 @@ function onKeydown(event: KeyboardEvent) {
     </LightTooltip>
   </div>
 
-  <div v-else @contextmenu="onTreeItemContextMenu">
+  <div v-else :class="{ 'sidebar-tree-item--sticky': stickyHeader }" @contextmenu="onTreeItemContextMenu">
     <LightTooltip :text="visibleLabel(node)" :disabled="isTooltipDisabled()" side="right" :side-offset="8" :delay="0" :close-delay="30" :surface="detailTooltip ? 'popover' : 'foreground'">
       <div
         ref="rowRef"
@@ -1399,7 +1399,6 @@ function onKeydown(event: KeyboardEvent) {
             'tree-item-active': selectionVisual.rowSelected,
             'tree-item-active--selection-set': selectionVisual.usesSelectionSetHighlight && selectionVisual.rowSelected,
             'tree-item-highlight': highlighted,
-            'sidebar-tree-item--sticky': stickyHeader,
           },
         ]"
         :tabindex="selectionVisual.selected || selectionVisual.multiSelected ? 0 : -1"
@@ -1635,7 +1634,6 @@ function onKeydown(event: KeyboardEvent) {
   top: 0;
   z-index: 2;
   background-color: var(--background);
-  border-bottom: 1px solid var(--border);
 }
 
 .tree-item-connection-tint:hover::before {