fix(client): tighten page tree vertical density

Reduce DocTree default rowHeight from 32px to 26px so sidebar page
tree rows pack closer together. The virtualizer uses rowHeight as the
row stride (estimateSize + translateY), and row content is only ~22px
tall, so the previous 32px left an ~8px gap between nodes. Both the
space tree and the shared (public) tree inherit the default, so both
become denser and stay consistent.

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

@@ -122,7 +122,11 @@ function DocTreeInner<T extends object>(
     selectedId,
     renderRow,
     indentPerLevel = 8,
-    rowHeight = 32,
+    // Compact vertical density: each virtualized row occupies exactly this
+    // many px (the virtualizer stride). Row content is ~22px (18px icon /
+    // 14px text / 20px action icons), so 26px keeps a small, even gap between
+    // nodes without clipping. Lower => denser tree.
+    rowHeight = 26,
     onMove,
     onToggle,
     onSelect,