SOURCES: cite the scientific origin, not the internal staging path

The data is TCGA/GDC -- public and citable on its own. The upstream staging
root said nothing the per-file relative paths below do not already carry.

SOURCES.md

@@ -7,15 +7,13 @@ re-formatted from experimental data.
 
 | Artifact | Origin | Format | Provenance |
 |---|---|---|---|
-| `samples.tar.gz` | TCGA tumour bulk RNA-seq → AIRR clonotypes (internal *staging* pipeline) | tar.gz of per-sample AIRR TSVs | **experimental** (RNA-derived receptor rearrangements) |
+| `samples.tar.gz` | TCGA tumour bulk RNA-seq → AIRR clonotypes (RNA-seq receptor profiling, Bolotin 2017) | tar.gz of per-sample AIRR TSVs | **experimental** (RNA-derived receptor rearrangements) |
 | `metadata.tsv` | join of the source tables below, restricted to the 9,591 AIRR samples | TSV, keyed by `sample_id` | **derived** |
 | `total_reads` (col) | GDC `rna_seq.genomic.gdc_realn.bam` `Total_Reads` | integer | **experimental** (raw library read total, all reads) |
 | `aligned_reads` (col) | GDC realigned-BAM `Aligned_Reads` | integer | **experimental** (genome-aligned subset) |
 | `metadata.hla.tsv` | HLA class-I: TCGA PanImmune (primary) ∪ OptiType-2017 fill, one row per donor | TSV, keyed by `subject_id`, `hla_source` col | **derived** (from experimental OptiType-based calls) |
 
-## Upstream sources (internal `staging`, 2025)
-
-Local root: `(internal staging)`
+## Upstream sources (internal staging, 2025)
 
 | Source | Path | Role |
 |---|---|---|