[feat][SFT] Return final Fireworks export evidence

Expose the promoted model and trainer cleanup manifest to downstream lifecycle tracking.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Signed-off-by: Bharat Mekala <155010017+bharatmekala@users.noreply.github.com>

Author: bharatmekala

skyrl/train/entrypoints/main_fireworks_sft.py

@@ -14,15 +14,15 @@
 from skyrl.train.fireworks_sft_trainer import FireworksSFTTrainer
 
 
-def run(cfg: SFTConfig) -> None:
+def run(cfg: SFTConfig) -> dict | None:
     """Run the native SFT loop without attaching to Ray."""
 
     validate_fireworks_sft_cfg(cfg)
     trainer = FireworksSFTTrainer(cfg, skyrl_cfg=build_skyrl_config_for_sft(cfg))
     try:
         trainer.setup()
         trainer.train()
-        trainer.export_final_model()
+        return trainer.export_final_model()
     except Exception as exc:
         if trainer.tracker is not None:
             trainer.tracker.log_exception(exc, step=trainer.global_step)

tests/train/test_fireworks_sft_trainer.py

@@ -321,14 +321,16 @@ def train(self):
 
         def export_final_model(self):
             events.append("export")
+            return {"model": "promoted"}
 
         def shutdown(self):
             events.append("shutdown")
 
     monkeypatch.setattr("skyrl.train.entrypoints.main_fireworks_sft.FireworksSFTTrainer", Trainer)
 
-    run(_cfg())
+    result = run(_cfg())
 
+    assert result == {"model": "promoted"}
     assert events == ["init", "setup", "train", "export", "shutdown"]