fix: agent streaming with new OpenAI models (#706)

.changeset/nasty-buttons-confess.md

.github/workflows/test.yml

packages/core/e2e/node/openai.e2e.ts

packages/core/e2e/node/snapshot/gpt-4-turbo.snap

packages/core/e2e/node/utils.ts

packages/core/src/agent/openai/worker.ts

packages/core/src/llm/open_ai.ts

packages/env/package.json

packages/env/src/index.polyfill.ts

packages/env/src/index.ts

pnpm-lock.yaml