[docs] ChatModelAgent quickstart uses outdated event field path

Describe the bug

The ChatModelAgent quickstart in README.md and README.zh_CN.md uses:

fmt.Println(event.Message.Content)

This does not match the current ADK event structure. In the current API, the message is exposed through event.Output.MessageOutput, so the example is outdated and does not reflect the current code.

To Reproduce

Steps to reproduce the behavior:

1. Open the ChatModelAgent quickstart in README.md
2. Follow the example with the current eino / adk API
3. Inspect the event type returned by runner.Query(...)
4. See that event.Message does not exist Expected behavior

The quickstart should use the current API, for example by reading the message from event.Output.MessageOutput and then accessing Content from the returned message.

Screenshots

Version:

main branch, introduced in README rewrite commit e328752

Additional context

This issue exists in both:

• README.md
• README.zh_CN.md

The current ADK types use AgentEvent -> AgentOutput -> MessageOutput.