Generate an AI meme image (paid, agent rail)

Generate an image from a text prompt via Grok Imagine. PAID endpoint (agent payment rails — no account needed; the payment is the auth). Attach proof via PAYMENT-SIGNATURE or X-PAYMENT header (base64 JSON x402 payload, USDC on Base) or Authorization: L402 <macaroon>:<preimage> (Lightning sats). Without proof the response is 402 with a dual-rail offer. Rate limited 30/min/IP. Returns 404 while payments are disabled. Prices: $0.08 standard / $0.20 quality (paid in sats over Lightning at the current BTC/USD rate, or in USDC on Base). Long-polls up to ~90s; on 202, retry with the SAME payment proof to resume — one payment delivers at most one image.