List dashboards

The pagination half of a v3 list's meta, shared by every paginated collection.

Deliberately open, and never an endpoint's meta by itself: an endpoint composes it with allOf and closes the result with unevaluatedProperties: false. A base that closed itself could not be extended — inside an allOf, additionalProperties: false sees a sibling branch's properties as additional and rejects them. An endpoint that adds nothing still wraps it, so no meta anywhere is open.

Every field here is required. A shared envelope that makes its fields optional is how v3's predecessor stopped honouring its own pagination contract without the schema gate noticing (ENG-2622): meta: {} — or no meta at all — validated cleanly while the endpoint returned nothing.