fix: step wise agent + examples (#594)

.changeset/four-ways-enjoy.md

examples/agent/step_wise_openai.ts

examples/agent/step_wise_query_tool.ts

examples/agent/step_wise_react.ts

packages/core/src/agent/runner/base.ts

packages/core/src/agent/types.ts

packages/core/src/llm/LLM.ts