fix(smolagents): give agent run span as more descriptive span name

[Zoe14]

Instead of having generic CodeAgent / ToolCallingAgent, now the log would show which specific agent

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Note

Set run span name to the agent's name if present, otherwise fall back to the class name.

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[Zoe14]

I have read the CLA Document and I hereby sign the CLA

[caroger]

hey @Zoe14 , thanks for the PR.

There is a simple formatting step you need to run to get your PR over the line - runuvx --from ruff==0.9.2 ruff check --fix . under the directoryopeninference/python/instrumentation/openinference-instrumentation-smolagents

[Zoe14]

can we merge this ? @caroger