feat: complete automatic mobile board UX

apps/docs/docs/management/api/index.mdx

@@ -82,6 +82,8 @@ The OpenAPI and MCP APIs include board management endpoints for common automatio
 - Set desktop and mobile home boards for the current user
 - Configure global board defaults such as public home boards and status behavior
 
+Board layout responses identify each layout with a `mobile`, `base`, or `custom` role. Mobile and Base are protected. Layout-saving clients must preserve existing roles, keep Mobile at breakpoint `0`, keep Base as the highest breakpoint, and use unique custom breakpoints between them. The layout save operation returns the canonical saved layouts, including server-generated IDs for new custom layouts. A non-Base layout can be regenerated from Base with the protected reset operation.
+
 Use the interactive API reference to inspect the exact request body for each endpoint under the `boards` and `settings` tags.
 
 ## Partial integration failures