Show HN: Grai – A deterministic cadence gate for AI drafts

Grai is a local-first HTML5 workbench that extracts a writer's "Voice DNA" from 5 to 20 past posts—measuring median sentence length, burstiness (CV), and rhythm floor—then audits AI-assisted drafts against 8 structural rules and a CV ≥ 0.32 floor in the browser. The shipped grai.html (618 KB) blocks direct API connections by default and runs in Copy-Paste mode, building prompts under 1,800 characters for Claude, ChatGPT, or Gemini, with a BYOK/Ollama path available by editing connect-src and rebuilding. It cites the LigoSocial dataset of 134,522 LinkedIn posts across 1,499 founder profiles over 3.5 years, reporting that arrow bullets rose 20.5x and "Here is why" openings rose 7.4x, and offers a free browser-based test plus paid editions ($79/yr Solo, $99/mo Agency).