README: rewrite intro to frame as RULER-inspired, explain near-duplicate task properly

README.md

@@ -109,16 +109,30 @@ configs:
 
 # Genome-NIAH
 
-A NIAH-style needle-in-a-haystack benchmark for genomic language models, with
-a DNA-specific **near-duplicate** distractor extension that's not in RULER.
+A long-context retrieval benchmark for genomic language models, **inspired by
+NIAH and RULER**.
+
+The plain `niah` task is a direct DNA analogue of RULER's `niah_single`:
+insert a random (KEY, VALUE) pair into a long real-genome haystack, append
+KEY at the end, and ask the model to generate VALUE. This gives a clean
+cliff diagnostic — the context length at which a model stops retrieving.
+
+To stress-test models that already pass plain NIAH, we developed a harder
+**near-duplicate** variant. Inspired by RULER's `niah_multikey` (random
+distractor pairs), we replace random distractors with **8 (KEY', VALUE')
+pairs whose KEY' differs from the target KEY by exactly Δ base pairs**
+(Hamming distance Δ = 1, 2, or 4). The model must distinguish the target
+key from 8 close-but-not-identical decoys — a fine-grained pattern-matching
+test that has biological relevance (DNA contains many similar-but-distinct
+motifs) and provides resolution beyond what plain NIAH can detect.
 
 ## Tasks
 
 | Task | What it tests |
 |---|---|
-| `niah` | Plain NIAH: insert (KEY, VALUE) at a random depth, query KEY → expect VALUE. The cliff diagnostic. |
-| `niah_neardup_d4` | NIAH + 8 distractor (KEY', VALUE') pairs where KEY' differs from KEY by 4 bp (83 % key identity). |
-| `niah_neardup_d2` | Same but Δ = 2 bp (92 % key identity). |
+| `niah` | Plain NIAH: insert (KEY, VALUE) at a depth, query KEY → expect VALUE. The cliff diagnostic. |
+| `niah_neardup_d4` | NIAH + 8 distractor (KEY', VALUE') pairs where KEY' differs from KEY by 4 bp (83 % key identity). Easiest harder tier. |
+| `niah_neardup_d2` | Same but Δ = 2 bp (92 % key identity). Cleanest separator between extension methods. |
 | `niah_neardup_d1` | Same but Δ = 1 bp (96 % key identity) — the discrimination test. |
 
 ## Context lengths