What is the largest ship in the Tau?

Could you please elaborate on the largest ship in the Tau? Is it a military vessel, a commercial carrier, or perhaps a scientific research platform? What sets it apart from other ships in terms of size, capabilities, and significance within the Tau's fleet? Additionally, are there any notable features or specifications that make it stand out as the most impressive vessel in the region? Understanding these details would provide valuable insights into the technological advancements and strategic priorities of the Tau.