Read the structure of a project's tab bar: every page and group, top to bottom, with their ids. Call this FIRST — every other tool in this group (`xtiles_update_page`, `xtiles_delete_page`, `xtiles_create_page_group`, `xtiles_update_page_group`, `xtiles_delete_page_group`, `xtiles_move_pages`) needs a `viewId` and/or `groupId` that only this call gives you. Each entry has `kind: "PAGE"` (a bare page, with `id`, `title`, `view_type`, `color`, `is_archived`) or `kind: "GROUP"` (a group of pages, with `id`, `title`, `color`, `group_type`, `system`, `is_archived`, and `pages`). Archived pages/groups (`is_archived: true`) are listed here too, not filtered out — this is the only way to find one again to unarchive it with `xtiles_update_page`/`xtiles_update_page_group`. A group with `system: true` is product-managed (the planner) — its `pages` field is OMITTED entirely, not an empty list, and you must never rename it, delete it, or move pages into or out of it. The API refuses such an attempt with a 409, but do not even try: treat every `system: true` group as read-only and invisible to the write tools in this group. Those omitted pages are planner days, addressed by date instead of by id: read one with `xtiles_get_planner_content` (period + date + this `projectId`), write to it with `xtiles_create_tiles_from_markdown_in_project_planner`.
