dashboard: SOTA prefill KPIs mislabel context (32k shown as 128; 4k shown as 32k)

[kurosawareiji7007-hub]

Summary

The public SOTA hero KPIs hardcode prefill context labels that do not match prefill_frontier_pp:

Card	Shown pp/s	Hardcoded label	Actual matching pp[] row
Qwen3.6	1282	"128 prefill baseline"	32k
Qwen3.5	16083	"32k prefill"	4k

The Qwen3.5 journey hint also compares the frontier to llama.cpp 32k ref_pp, so the "% of llama.cpp" is cross-context and misleading.

Expected

Derive the label and ref_pp from the pp[] row whose pp matches prefill_frontier_pp.

Scope

dashboard/index.html only. No GPU / no runtime/kernels/moe / no dashboard/data.json.