Python: [Python] Agent v2 client requires choice between creating a new version each time, or pinning a version

[tonybaloney]

The API for Agent v2 has two options:

1. Provide an agent_version and use that
2. Have a new version of the agent created each time it is run

https://github.com/microsoft/agent-framework/blob/feature-python-foundry-agents/python/packages/azure-ai/agent_framework_azure_ai/_client.py#L192

The second option takes about 2-3 seconds to create a new agent version and after running the agent tens/hundreds of times you would have hundreds of identical versions.

The alternative requires setting a version (e.g. 1) and that requires the agent to have existed before hand.

Neither are ideal. There should be a declarative, idempotent API which doesn't create a new agent version each time.

Also, the agent_version is typed as a string, but it is a number.