fix(litellm): generate toolUseId when missing from provider

[Ratish1]

Description

LiteLLM returns null for the tool call id field, causing toolUseId to be None in the resulting event stream. This PR ensures that a valid UUID is generated and assigned to the tool call delta if the provider returns a missing or null ID.

Changes:

• Modified LiteLLMModel.stream to check for a missing id on the first tool delta and generate a new UUID if needed.
• Added a unit test test_stream_generates_tool_call_id_when_null to verify this behavior.

Related Issues

Fixes #1259

Documentation PR

N/A

Type of Change

Bug fix

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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