Tiled batch merge

Implement and measure a tiled batch merge for misi queries that reuses streamed posting data across a batch and quantifies the resulting reduction in posting-read traffic and total computational cost.

Background

For a batch of B queries, the paper observes that the posting matrix could be streamed once and accumulated as a tiled sparse product, reducing posting-read traffic per query after the batch exceeds a threshold. However, vote additions remain irreducible, so an implementation and empirical evaluation are needed to determine the actual end-to-end benefit.