Standardize pagination across all list operations

[bokelley]

Problem

List operations have inconsistent pagination support:

Operation	Pagination	Style
list_creatives	Yes	Offset-based (limit/offset, has_more, total_pages)
list_property_lists	Yes	Cursor-based (max_results/cursor, has_more)
list_accounts	None	Simple array
get_products	None	Simple array

Two operations lack pagination entirely, and the two that have it use different patterns (offset vs cursor).

Proposal

1. Add pagination to get_products and list_accounts — both can return unbounded result sets from platforms with many products or retailer accounts.

2. Standardize on one pagination pattern. Cursor-based is generally better for large or frequently-changing datasets (which ad platforms tend to be), and avoids the consistency issues of offset-based pagination.

   Suggested standard pattern for requests:

   {
     "pagination": {
       "max_results": 50,
       "cursor": "optional_cursor_string"
     }
   }

   Suggested standard pattern for responses:

   {
     "pagination": {
       "total_count": 142,
       "returned_count": 50,
       "has_more": true,
       "cursor": "next_page_cursor"
     }
   }

3. Migrate list_creatives from offset-based to cursor-based for consistency (breaking change, would need a major version bump or deprecation period).

Related

Adapter implementation issue: adcontextprotocol/adcp-client#222