[ci] Ensure unit tests run for nested Go modules

Ensure CI unit testing is running against top-level as well as all nested Go modules in the agent repo.

Start by locating the repository's CI workflow definitions and every go.mod in the agent repo, then compare current unit-test coverage for the top-level and nested modules. Run the existing CI or unit-test entry point if documented, and consider the work done when CI exercises unit tests for each module.

Written by the indexing model from the issue text.