/**
 * Needle Engine AI skill installer.
 *
 * Writes a Needle Engine skill to `<dir>/skills/needle-engine/SKILL.md`
 * for each supported AI agent directory (`.claude/`, `.github/`, `.agents/`).
 * Both Claude Code and GitHub Copilot auto-load skills based on their
 * description frontmatter, so the AI agent will automatically have Needle
 * Engine context when working in the project.
 *
 * The skill is only written if at least one of the supported directories
 * already exists in the project root (i.e. the developer is already using
 * an AI coding agent).
 * Old skill files are always overwritten so the skill stays up to date with
 * the engine version.
 *
 * @param {"build" | "serve"} command
 * @param {{} | undefined | null} config
 * @param {import('../types/index.js').userSettings} userSettings
 * @returns {import('vite').Plugin | null}
 */
export function needleAI(command: "build" | "serve", config: {} | undefined | null, userSettings: import("../types/index.js").userSettings): import("vite").Plugin | null;