* chore: use ConfigurationError when package_dir is outside cwd
Replace a generic Exception with errors. ConfigurationError when package_dir is not inside the working directory. This makes the error type consistent with the project's error handling and allows the CLI to treat this as a fatal error with the expected exit behavior.
* test: merge linux package_dir test into linux_build_steps_test
Fold the standalone linux_build_test.py into the existing
linux_build_steps_test.py, which already covers the linux platform
build orchestration. Reuses the file's existing import boilerplate and
module-qualified build() call style.
Assisted-by: ClaudeCode:claude-opus-4.8
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---------
Co-authored-by: Henry Schreiner <henryfs@princeton.edu>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
