Fetch one Weibo post's full detail plus up to 10 pages of comments (~150 total) with cursor-based pagination. Pass numeric postId (+ optional mid) from upstream feeds.
Rebrand (no API change): rename internal client to UpstreamClient; env vars TIKHUB_API_KEY / TIKHUB_BASE_URL → UPSTREAM_API_KEY / UPSTREAM_BASE_URL; file src/tikhub_client.js → src/upstream_client.js. Per our internal SOP §100 (no upstream name in user-facing surfaces), existing 0.1.2 runs keep working until the next push.
Fix (bonus): test/integration.js was the hot-search template (called fetchTrendTop + intervalSeconds); replaced with two post-detail-specific tests covering fetchPostDetail (single post object) and fetchPostComments (first page). 7/7 unit + 2/2 integration tests PASS.