Public search query: cursor pagination

Tags, author filters, and document types change what a search means. I want examples that show how these filters combine and whether a blank query is allowed. Unknown filter values should get a clear response rather than quietly disappearing.

No matches, filters excluding everything, unavailable retrieval, and unauthorized content are different outcomes. I would keep those distinctions in the API and show the user a next step that fits the actual condition. A generic empty illustration should not hide a service failure.