Bitable Build Child Rows

Atomically create N child rows + append their ids to a parent link cell.

Called by skill workers that fan out a 1→N split (e.g. video_split turns a reference video into clip rows). Runs under a single transaction so a caller failure leaves the parent cell unchanged and the child rows either all created or none.

Body (JSON, matching BuildChildRows schema): parent_table_id uuid parent_row_id uuid parent_col_id str — must be a link column on the parent table child_rows [{data: dict, order_key?: str}, ...] (1..200)

Response: {child_row_ids: [uuid, ...]}