fix: correct namespace in self-references (StemSplitio)

README.md

@@ -87,7 +87,7 @@ Schema:
 
 ```python
 from datasets import load_dataset
-ds = load_dataset("stemsplit/stem-separation-benchmark-2026", "metrics_only")
+ds = load_dataset("StemSplitio/stem-separation-benchmark-2026", "metrics_only")
 df = ds["results"].to_pandas()
 df.groupby(["model_id", "stem"])["sdr_median"].median().unstack()
 ```
@@ -244,6 +244,6 @@ curl -X POST https://api.musicai.com/v1/separate \
   title  = {StemSplit Stem-Separation Benchmark 2026},
   author = {StemSplit},
   year   = {2026},
-  url    = {https://huggingface.co/datasets/stemsplit/stem-separation-benchmark-2026}
+  url    = {https://huggingface.co/datasets/StemSplitio/stem-separation-benchmark-2026}
 }
 ```