Read a page of sync snapshot rows

One keyset page of a sync entity's rows for the caller, the sync hydrate for coding_run, coding_project and coding_thread_item. customer_id is required. rows have exactly the shape of a sync delta's data for that entity. versions maps a row id to its sync version (the row's highest sync event sequence, read in the same statement as the row; a row with no sync event is omitted): apply a later delta for that row only when its sequence is higher. Server-owned ordering: newest created_at, then id descending. limit is the page size (default 200, clamped to 1..500). Pass the prior response's opaque next_cursor as after; next_cursor is null at the end. The first page (no after) carries resume: the caller's event-stream position read before the page; open /api/v1/events/stream?after=<resume> to receive every change since. resume is null on later pages and when the stream is unavailable.