Add User-Agent header for Anthropic API calls

[mikelambert]

Description

Passes User-Agent: llama-index-llms-anthropic/{version} to the Anthropic SDK so Anthropic can identify traffic from LlamaIndex integrations.

Version Bump?

Did I bump the version in the pyproject.toml file of the package I am updating? (Except for the llama-index-core package)

• Yes

Type of Change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• I added new unit tests to cover this change

Suggested Checklist:

• I have performed a self-review of my own code
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I ran uv run make format; uv run make lint to appease the lint gods

[dosubot]

Related Documentation

Checked 0 published document(s) in 1 knowledge base(s). No updates required.

^{How did I do? Any feedback?}  

[mikelambert]

I see a failure on python3.9 on CI, but it appears unrelated to my change:

.venv/lib/python3.9/site-packages/llama_index/core/indices/prompt_helper.py:558: in ChatPromptHelper
    llm: LLM | None = None,
E   TypeError: unsupported operand type(s) for |: 'ModelMetaclass' and 'NoneType'

I suspect someone else submitted a python-3.10-ism here, but that this isn't blocking for merging?