PR #320 changed SiteNode.children from embedded BuildingNode/ItemNode
objects to flat string[] IDs. PR #325 updated the runtime call sites
but missed the three scene templates, which still mutated the site
node's children array to embed full building objects after building
the flat dict. This caused AnyNode.safeParse to fail for site_empty,
site_2br, and site_garden in bun test --cwd packages/mcp.
Remove the obsolete mutation blocks; each template already initialises
site.children with the correct string id (e.g. ['building_empty']).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
