Add config fixture and unit test validating its fields

[binrogithub]

Motivation

• Provide a local YAML fixture containing region and endpoint.base_domain for tests to consume without relying on secrets or external network access.

Description

• Add tests/fixtures/config.yaml with region: us-east-1 and endpoint: base_domain: example.test, and add tests/fixtures_unittest.py which loads the fixture and asserts the presence of region, endpoint: and base_domain using regex checks.

Testing

• No automated test suite was executed as part of this change; the new unit test file tests/fixtures_unittest.py was added to the repository but not run.

---

Codex Task