fix: make strict Clippy pass across CLI targets

[blackopsrepl]

Summary

• flatten the nested CLI test modules that triggered clippy::module_inception
• keep the existing test coverage intact while preserving the current module layout
• validate the CLI crate on the release/0.6.0 line

Validation

• cargo clippy --workspace --all-targets -- -D warnings
• cargo test -p solverforge-cli

Closes #4