Add dimension metadata support

[Muizzkolapo]

Summary

This is a simple change to add dimension metadata support across the Semantic Layer tool response.

What Changed

• Added config.meta to the dimensions GraphQL query and surfaced it in DimensionToolResponse.
• Updated get_dimensions prompt documentation to describe the metadata field.
• Added a unit test to verify metadata extraction and missing config handling.
• Added a lightweight integration assertion for metadata presence.

BEFORE

AFTER

Why

As stated in this gh issue #437. The dimension metadata already exists in the Semantic Layer API but wasn’t being returned. Exposing it improves downstream decision‑making and keeps parity with metrics.

Related Issues

Closes #437
Related to #437

Checklist

• I have performed a self-review of my code
• I have made corresponding changes to the documentation (in https://github.com/dbt-labs/docs.getdbt.com) if required -- Mention it here
• 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

Additional Notes

[DevonFulcher]

Nice!