fix(client): compact page tree + fix selection highlight alignment

Reduce DocTree row stride from 32px to 26px for a denser sidebar tree,
and fix the selection/hover highlight that looked unbalanced at the
tighter spacing.

Root causes:
- The virtualized <li> had no explicit height, so `.node`'s height:100%
  collapsed to content height; combined with the asymmetric
  `[role="treeitem"] { padding-bottom: 2px }` rule, row content was
  pushed to the top of the highlight pill (icon glued to the top edge).
- NodeMenu / CreateNode action icons used the default Mantine ActionIcon
  size (md = 28px), overflowing the tighter 26px row stride onto
  neighbouring rows.

Changes:
- doc-tree.tsx: rowHeight 32 -> 26; give each row <li> a definite
  height = rowHeight.
- tree.module.css: rowWrapper fills the slot (height:100%); node pill is
  inset and vertically centered (height: calc(100% - 4px)); drop the
  asymmetric [role="treeitem"] padding-bottom.
- space-tree-node-menu.tsx / space-tree-row.tsx: action icons size={20}.
- share.module.css: drop now-dead .treeNode padding-bottom override.

Verified in an isolated browser harness: highlight content is centered
(2.8/2.8px) and nothing overflows the row stride.

apps/client/src/features/page/tree/components/doc-tree.tsx

@@ -510,6 +510,12 @@ function DocTreeInner<T extends object>(
                 top: 0,
                 left: 0,
                 width: '100%',
+                // Give the row slot the exact virtualizer stride height so the
+                // inner highlight can fill and vertically center within it.
+                // Without a definite height here, `.node`'s `height: 100%`
+                // collapses to content height and the selection pill ends up
+                // top-aligned (asymmetric) inside the stride.
+                height: rowHeight,
                 transform: `translateY(${virtualItem.start}px)`,
               }}
             >

apps/client/src/features/page/tree/components/space-tree-node-menu.tsx

@@ -124,6 +124,7 @@ export function NodeMenu({ node, canEdit }: NodeMenuProps) {
       <Menu shadow="md" width={200}>
         <Menu.Target>
           <ActionIcon
+            size={20}
             variant="subtle"
             color="gray"
             className={classes.actionIcon}

apps/client/src/features/page/tree/components/space-tree-row.tsx

@@ -273,6 +273,7 @@ function CreateNode({
 
   return (
     <ActionIcon
+      size={20}
       variant="subtle"
       color="gray"
       className={classes.actionIcon}

apps/client/src/features/page/tree/styles/tree.module.css

@@ -17,7 +17,11 @@
     border-radius: 4px;
     display: flex;
     align-items: center;
-    height: 100%;
+    /* Inset the highlight pill by 2px top + 2px bottom inside the full-height
+       row slot. rowWrapper (height: 100%, align-items: center) vertically
+       centers this pill in the stride, giving an even gap between rows and
+       symmetric padding around the row content. */
+    height: calc(100% - 4px);
     width: 100%;
     text-decoration: none;
     color: light-dark(var(--mantine-color-gray-7), var(--mantine-color-dark-0));
@@ -77,10 +81,6 @@
     display: flex;
 }
 
-[role="treeitem"] {
-    padding-bottom: 2px;
-}
-
 /* Strip the browser's default <ul> bullet + indent from the DocTree
    <ul role="tree"> and nested <ul role="group"> nodes. The tree's own indent
    is driven by paddingLeft on .rowWrapper. */
@@ -98,6 +98,9 @@
     display: flex;
     align-items: center;
     border-radius: 4px;
+    /* Fill the full row slot (the <li> is sized to the virtualizer stride) so
+       align-items: center can vertically center the inset `.node` pill. */
+    height: 100%;
 }
 
 .node[data-dragging="true"] {

apps/client/src/features/share/components/share.module.css

@@ -10,7 +10,6 @@
 .treeNode {
   text-decoration: none;
   user-select: none;
-  padding-bottom: 0;
 }
 
 .navbar,