I'm afraid, I would stop the aircraft. Use standard cabin calls and evacuate. Then face the music and dance.
For an unconfirmed fire indication? Think about the risk that someone might get seriously injured during the evacuation.
Cargo smoke detection and fire suppression didn't become mandatory until recently. A lot of aircrafts are still flying without these systems and that include modern aircrafts like early 737NGs. At my previous employer most of the aircrafts didn't have it.
Would you taxi the aircraft to the terminal aero bridge or disembark using stairs away from the building?
I don't think you will be able to make that decision. With high probability the airport have their own procedures for such situation. And if in a civilized part of the world, I am sure you will have stairs in the blink of an eye.