fix logging and set default logging level to ERROR

[wzxxing]

Summary

Changes

Please provide a summary of what's being changed

Change the default log level to ERROR otherwise the log is too verbose.

User experience

Please share what the user experience looks like before and after this change

Some MCP client (such as cline) seems to have issues if stdio servers log to stderr during the initialize phase.

Checklist

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• I have reviewed the contributing guidelines
• I have performed a self-review of this change
• Changes have been tested
• Changes are documented

Is this a breaking change? (Y/N)

• Yes
• No

Please add details about how this change was tested.

• Did integration tests succeed?
• If the feature is a new use case, is it necessary to add a new integration test case?

Acknowledgment

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