cleanup StorageW1R3 structure

The code for this test should live in a sub-directory of `Sources/`, and be implemented as a library. That way we can write unit tests for some of the components.

The main program should be a small executable target with just a main function that calls the main class.

The integration test should just be a regular `@Suite` that configures and invokes the main class.

Locate the StorageW1R3 test code and the current package structure under Sources/, then inspect how the main program and integration test are wired. Done means the implementation is a library, the executable target contains only a main function calling the main class, and the integration test is a regular @Suite that configures and invokes that class.

Written by the indexing model from the issue text.