feat(mcp): add hierarchical tree mode to list_pages

list_pages gains an opt-in `tree` parameter on both surfaces (the
@docmost/mcp server tool and the AI-chat agent tool), which share the
same DocmostClient.listPages. Default behavior (recent-by-updatedAt flat
list) is unchanged.

- client.ts: listPages(spaceId?, limit=50, tree=false); when tree is
  true it requires spaceId (throws a specific error otherwise), walks the
  sidebar tree via the existing bounded/cycle-safe enumerateSpacePages,
  and returns a nested tree; limit is ignored in tree mode.
- lib/tree.ts: new pure buildPageTree() — lean nodes { id, slugId, title,
  children? }, children sorted by position (code-unit order), orphans
  promoted to roots, cycle-safe.
- index.ts + ai-chat-tools.service.ts: expose `tree` in the tool schemas
  and descriptions; docmost-client.loader.ts: mirror the new signature.
- tests: add packages/mcp/test/unit/tree.test.mjs (nesting, ordering,
  lean shape, orphan promotion, cycle/self-reference safety).
- rebuild @docmost/mcp (build/ is tracked and loaded at runtime).

packages/mcp/build/client.js

@@ -9,6 +9,7 @@ import WebSocket from "ws";
 import { convertProseMirrorToMarkdown } from "./lib/markdown-converter.js";
 import { updatePageContentRealtime, replacePageContent, markdownToProseMirror, mutatePageContent, buildCollabWsUrl, assertYjsEncodable, } from "./lib/collaboration.js";
 import { docmostExtensions } from "./lib/docmost-schema.js";
+import { buildPageTree } from "./lib/tree.js";
 import { serializeDocmostMarkdown, parseDocmostMarkdown, } from "./lib/markdown-document.js";
 import { replaceNodeById, deleteNodeById, insertNodeRelative, buildOutline, getNodeByRef, readTable, insertTableRow, deleteTableRow, updateTableCell, } from "./lib/node-ops.js";
 import { withPageLock } from "./lib/page-lock.js";
@@ -440,12 +441,29 @@ export class DocmostClient {
         return spaces.map((space) => filterSpace(space));
     }
     /**
-     * List most recent pages (bounded). Fetching the whole space can exceed
-     * MCP response/time limits on large instances, so a single bounded page
-     * of results is returned (default 50, max 100).
+     * List pages in one of two modes.
+     *
+     * Default (`tree` false): most recent pages by updatedAt (descending),
+     * bounded. Fetching the whole space can exceed MCP response/time limits on
+     * large instances, so a single bounded page of results is returned (default
+     * 50, max 100) via the `/pages/recent` feed.
+     *
+     * Tree (`tree` true): the space's FULL page hierarchy as a nested tree (each
+     * node has a `children` array). This mode REQUIRES `spaceId` (a page tree is
+     * scoped to one space) and IGNORES `limit` — the whole hierarchy is returned.
+     * It walks the sidebar tree via `enumerateSpacePages`, which performs N
+     * sidebar requests and is bounded by that method's 10000-node cap (and skips
+     * soft-deleted pages server-side).
      */
-    async listPages(spaceId, limit = 50) {
+    async listPages(spaceId, limit = 50, tree = false) {
         await this.ensureAuthenticated();
+        if (tree) {
+            if (!spaceId) {
+                throw new Error("list_pages: tree mode requires a spaceId (a page tree is scoped to one space). Pass spaceId, or omit tree to get the recent-pages list.");
+            }
+            const nodes = await this.enumerateSpacePages(spaceId);
+            return buildPageTree(nodes);
+        }
         const clampedLimit = Math.max(1, Math.min(100, limit));
         const payload = { limit: clampedLimit, page: 1 };
         if (spaceId)