docs(api): fix smart list available options

[rectifyer]

Summary

Fixes the smart lists documentation inaccuracies reported in #881. The docs described path and query params the API does not implement, and two endpoints linked to an items method that does not exist.

Changes

Fixed broken doc links. The "Get smart list" and "Get a user's smart lists" descriptions pointed to /users/:id/smart-lists/:list_id/items, which was never implemented. Smart list slugs are globally unique, so items are served by the top-level /smart-lists/:list_id/items method. Both links now point there.

Removed the type, sort_by, and sort_how path params from "Get smart list items". Audited against the worker implementation: the route declares all three as optional and the handler never reads them. They had no effect on the response. A smart list is targeted to a single media_type, so its items always match that type and a type filter is not meaningful. The canonical path is now /smart-lists/:list_id/items.

Removed unsupported query params. start_date, end_date, and ignore_collected are not parsed by the worker's filter handling, so they are omitted from the items query schema. The shared schemas are untouched for other endpoints.

Verification

• deno fmt --check and deno lint pass on the edited files
• deno check passes on both contract files
• deno task openapi:validate passes

Closes #881