Landing page becomes an agent launcher: paste a docs URL, get a prompt

The hero is one search box. A docs URL, a partial URL or a tool name turns into a prompt for Claude Code, Cursor or Codex. The prompt has the agent check Docker, install FirstRun, run the quickstart, narrate the break and the fix, ask before opening the PR with firstrun pr, and end with the share link that run.html replays. Everything runs in the browser.