Anthropic adapter

import Anthropic from "@anthropic-ai/sdk";
import { meter } from "@amit641/llmmeter/anthropic";

const anthropic = meter(new Anthropic());

const r = await anthropic.messages.create({
  model: "claude-3-5-sonnet-latest",
  max_tokens: 200,
  messages: [{ role: "user", content: "Hello!" }],
});

Wraps messages.create for both non-streaming and streaming calls. Parses Anthropic's typed event stream (message_start, content_block_delta, message_delta) to extract input, output, and cache_read_input_tokens (used for prompt caching).