chore: scaffold VLM tracing guide

[vaishnavidesai09]

Closes #49

Checklist

• Linked to its tracking issue (commented to claim it before starting)
• Example is in the right bucket (guides)
• Folder name is lowercase_with_underscores
• README.md has all required sections; index tables updated if examples were added/renamed/removed
• uv run ruff check . and uv run ruff format --check . are clean
• No credentials or .env files committed
• Dependencies declared in pyproject.toml (uv project); no requirements.txt, no committed uv.lock
• OPIK_PROJECT_NAME is set — defined in a notebook cell
• Examples that call LLMs use litellm and read OPIK_EXAMPLES_MODEL
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