Unit test suite should depend on component under test

The wiring between a unit test suite and the component under test should use dependency resolution instead of ad hoc connections. This has some upsides:

- The implementation is consistent regardless of whether the test suite and component under test are in the same project or elsewhere.
- The connection is more visible to tooling and reporting.
- Variant aware goodness can be applied to select the target variant for the component under test.

The issue names no files, tests, or entry points. Start by locating the unit-test-to-component wiring and the existing dependency-resolution path; done means the connection uses dependency resolution and supports cross-project components, tooling visibility, and variant selection.

Written by the indexing model from the issue text.