refactor(tree): borrow cleanups from the sibling expand-all impl

- extract collectAllIds / collectBranchIds into tree/utils and use them in
  space-tree.tsx instead of inline closures
- drop the duplicate SidebarPageTreeDto, reuse the existing SidebarPageDto
  for the /pages/tree endpoint
- type the getSpaceTree client call as api.post<{ items: IPage[] }>

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/client/src/features/page/services/page-service.ts

@@ -96,7 +96,7 @@ export async function getSpaceTree(params: {
   spaceId: string;
   pageId?: string;
 }): Promise<IPage[]> {
-  const req = await api.post("/pages/tree", params);
+  const req = await api.post<{ items: IPage[] }>("/pages/tree", params);
   return req.data.items;
 }
 

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

@@ -25,6 +25,8 @@ import {
   buildTree,
   buildTreeWithChildren,
   mergeRootTrees,
+  collectAllIds,
+  collectBranchIds,
 } from "@/features/page/tree/utils/utils.ts";
 import { SpaceTreeNode } from "@/features/page/tree/types.ts";
 import { treeModel } from "@/features/page/tree/model/tree-model";
@@ -226,16 +228,7 @@ const SpaceTree = forwardRef<SpaceTreeApi, SpaceTreeProps>(function SpaceTree(
       });
 
       // Open every branch node (node with children) of the current space only.
-      const branchIds: string[] = [];
-      const collectBranchIds = (nodes: SpaceTreeNode[]) => {
-        for (const n of nodes) {
-          if (n.children && n.children.length > 0) {
-            branchIds.push(n.id);
-            collectBranchIds(n.children);
-          }
-        }
-      };
-      collectBranchIds(fullTree);
+      const branchIds = collectBranchIds(fullTree);
 
       setOpenTreeNodes((prev) => {
         const next = { ...prev };
@@ -260,14 +253,7 @@ const SpaceTree = forwardRef<SpaceTreeApi, SpaceTreeProps>(function SpaceTree(
   const collapseAll = useCallback(() => {
     // The open-map is shared across spaces; collapse only current-space ids so
     // other spaces' expanded state is left intact.
-    const ids = new Set<string>();
-    const walk = (nodes: SpaceTreeNode[]) => {
-      for (const n of nodes) {
-        ids.add(n.id);
-        if (n.children?.length) walk(n.children);
-      }
-    };
-    walk(filteredData);
+    const ids = collectAllIds(filteredData);
 
     setOpenTreeNodes((prev) => {
       const next = { ...prev };

apps/client/src/features/page/tree/utils/utils.ts

@@ -216,3 +216,33 @@ export function mergeRootTrees(
 
   return sortPositionKeys(merged);
 }
+
+// Collect every node id in the tree (roots, branches, leaves). Used by
+// collapseAll to clear the open-state map for all current-space nodes.
+export function collectAllIds(nodes: SpaceTreeNode[]): string[] {
+  const ids: string[] = [];
+  const walk = (list: SpaceTreeNode[]) => {
+    for (const n of list) {
+      ids.push(n.id);
+      if (n.children?.length) walk(n.children);
+    }
+  };
+  walk(nodes);
+  return ids;
+}
+
+// Collect ids of branch nodes (nodes that have children). Used by expandAll to
+// open every branch in the open-state map; leaves need no entry.
+export function collectBranchIds(nodes: SpaceTreeNode[]): string[] {
+  const ids: string[] = [];
+  const walk = (list: SpaceTreeNode[]) => {
+    for (const n of list) {
+      if (n.children?.length) {
+        ids.push(n.id);
+        walk(n.children);
+      }
+    }
+  };
+  walk(nodes);
+  return ids;
+}