fix: only run unit tests during Nix build, skip integration tests

Changed from selectively skipping test modules to running only --lib
tests (unit tests). This is cleaner and more maintainable.

Integration tests (tests/*.rs) require:
- git binary in PATH
- Ability to spawn subprocesses
- Network access for some tests
- TestRelay fixture (spawns ngit-grasp)

These requirements don't work in the Nix sandbox, so we run only
unit tests (--lib) during package build. Full integration test suite
runs in environments where git is available:
- Local dev (nix develop includes git)
- CI/CD (git installed)
- Manual testing (cargo test runs all tests)

0 files changed, 0 insertions, 0 deletions