Allow callers to pass additional systemctl flags (e.g. --no-block,
--force) via variadic string args on every exported function.
This is backward-compatible: existing callers without extra args
continue to work unchanged.
Introduces a prepareArgs helper to centralize argument construction,
replacing the duplicated args/UserMode pattern across all functions.
Closes#2
* refactor: clean up unused code, fix typos, improve docs
- Remove unused 'killed' const and 'unitTypes' var (staticcheck U1000)
- Replace regexp with strings.TrimSuffix+switch in isFailed for consistency
- Fix typo: 'programatically' -> 'programmatically'
- Fix typo: 'an an int' -> 'as an int' in README and helpers.go
- Add missing godoc comments on exported helper functions
- Bump minimum Go version from 1.18 to 1.21
* refactor: use unused constants instead of removing them
- Export unitTypes as UnitTypes and add HasValidUnitSuffix helper
- Use killed const (exit code 130) in execute() to detect SIGINT
- Update go.mod to go 1.26
