drop unsupported TCGA library-prep claim; cite GDC pipeline harmonization quote instead

README.md

@@ -30,7 +30,7 @@ National Cancer Institute (NCI) Genomic Data Commons (GDC). One HuggingFace
 (HF) subset per TCGA project; one row per patient.
 
 - **Projects included:** `TCGA-CHOL`, `TCGA-DLBC`, `TCGA-LUAD`
-- **Generated:** 2026-05-04 23:16:21 UTC
+- **Generated:** 2026-05-04 23:29:28 UTC
 - **Source:** GDC `/cases` endpoint, open-access tier only.
 - **Schema:** derived from the [GDC Data Dictionary][gdc-dict]; the live
   dictionary the GDC was serving when the data was fetched is hashed into
@@ -77,8 +77,10 @@ tree:
   record has the STAR per-feature quality-control counts `N_unmapped`,
   `N_multimapping`, `N_noFeature`, `N_ambiguous` lifted from the source
   Tab-Separated Values (TSV) file onto the row as scalar fields. The
-  `stranded_first` / `stranded_second` columns are dropped — TCGA used
-  unstranded library prep, so they're zero or unused.
+  `stranded_first` / `stranded_second` columns are dropped — the GDC
+  pipeline harmonizes by [treating all RNA-Seq reads as
+  unstranded](https://docs.gdc.cancer.gov/Data/Bioinformatics_Pipelines/Expression_mRNA_Pipeline/),
+  so `unstranded` is the canonical column.
 
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