Add Keygate capability-speed-price frontier report to §6

[kygate-ai]

Adds one data report to §6 · Benchmark vs. eval.

Entry: 哪些文本模型没有被全面超过？能力、速度与 API 价格三维数据报告 — Keygate · data report (Chinese)

Why it belongs: The report applies a disclosed July 2026 screening rule: 590 raw records narrow to 260 active text models, then to 70 complete, non-estimated candidates using one 7:2:1 API price formula. A three-objective non-dominance check leaves 16 candidates. It is a concrete demonstration of how one aggregate ranking can hide capability–speed–price trade-offs, and it states exclusions and limits rather than declaring an overall winner.

• Canonical public report reviewed
• One README entry in the recent block of §6
• URL and annotation follow CONTRIBUTING.md
• Caveat: the report publishes the screening rules and all 16 frontier rows, but not a separate frozen download of all 70 input rows
• Disclosure: I maintain Keygate