fix(server,mcp): repair createPage import and sidebar subpages lookup

createPage always failed with "generateJSON can only be used in a Node
environment". Root cause: the MCP module (packages/mcp/.../collaboration.ts)
sets `global.window = dom.window` (jsdom) at load time and is imported
in-process by the server's AI-chat tools, leaking a global `window` into the
Node process. The server's self-contained ProseMirror helpers guarded with
`if (typeof window !== 'undefined') throw`, which then became a false positive
and broke POST /pages/import (the endpoint createPage calls).

- server: drop the vestigial `typeof window` guard in generateJSON.ts and
  generateHTML.ts; both helpers create their own happy-dom Window and never
  read the global one. Replace it with an explanatory comment.
- mcp: in DocmostClient.getPage, pass the resolved UUID (resultData.id) to
  listSidebarPages instead of the original pageId, which may be a slugId and
  triggered a Postgres "invalid input syntax for type uuid" (and a silent
  empty subpages list).

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

packages/mcp/src/client.ts

@@ -732,7 +732,9 @@ export class DocmostClient {
     // Always fetch subpages to provide context to the agent
     let subpages: any[] = [];
     try {
-      subpages = await this.listSidebarPages(resultData.spaceId, pageId);
+      // `pageId` may be a slugId, but the sidebar-pages endpoint requires the
+      // UUID; `resultData.id` holds the resolved UUID returned by getPageRaw.
+      subpages = await this.listSidebarPages(resultData.spaceId, resultData.id);
     } catch (e: any) {
       console.warn("Failed to fetch subpages:", e);
     }