fix implementation to work correctly in mruby:
- use String#% instead of sprintf for formatting
- use $stdout directly for output instead of bare print/puts
- add nil check for $stdout to handle test environments
- use Object.const_defined? instead of defined? keyword
- create new Tms instance with label instead of instance_variable_set
- add dependencies: mruby-sprintf and mruby-io
Co-authored-by: Claude <noreply@anthropic.com>