tests/cli/add-from-fs(refactor): Rewrite tests following vcspull conventions

why: Tests didn't follow established vcspull testing patterns and had logging issues
what:
- Convert to parameterized tests using AddFromFsFixture(NamedTuple)
- Test through CLI entry point for integration testing
- Add helper functions setup_git_repo() and clone_repo() for test setup
- Add clear_logging_handlers fixture to prevent stream closure issues
- Remove caplog.set_level() calls that were causing handler conflicts
- Improve test organization and maintain full coverage

refs: #tests

Author: tony