Add anthropic to dev dependencies for LLM smoke tests

[JoeCardoso13]

Problem

The scaffolded tests-integration/test_skill_llm.py imports anthropic, but anthropic is not listed in the dev dependencies in pyproject.toml. Running make test-llm immediately fails with ModuleNotFoundError: No module named 'anthropic'.

Proposed fix

Add anthropic>=0.40.0 to the [dependency-groups] dev section in pyproject.toml.