models - openai - do not accept b64 images

[pgrayy]

Description

Following up on #251 to stop accepting base64 encoded images in the OpenAI model provider. For more details, see #252.

Related Issues

#252

Type of Change

• Bug fix
• New feature
• Breaking change: This is intentional and was preceded by a log warning to users.
• Documentation update
• Other (please describe):

Testing

How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli

• I ran hatch run prepare

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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[zastrowm]

Update #253 with the recommended text/bullet-point for this breaking change. The last time we were gathering breaking-changes, it was up to the oncall to figure out the wordage, but ideally we'd be doing that as we go.