Document cross-platform repository grouping

README.md

@@ -29,5 +29,5 @@ This version contains open-source ArkTS function-comment pairs from repositories
 
 Queries are globally unique: after cleaning, only one example is retained for each exact `docstring`.
 
-- `repo_split_balanced`: repository-isolated and approximately 80%/10%/10% by example count.
+- `repo_split_balanced`: repository-isolated by normalized `nwo` (platform is not part of the repository key) and approximately 80%/10%/10% by example count.
 - `random_shuffle`: shuffled with seed `20260714` and split 80%/10%/10%.