ModStatusKit 0.1.5

ModStatusKit 0.1.5 adds optional server-declared public version mismatch severity.\n\nHighlights:\n- Add VersionMismatchSeverity.WARN and BREAKING.\n- Add StatusTone.RED for server-declared breaking public/base version mismatches.\n- Keep default version mismatch behavior orange/WARN.\n- Keep build mismatch diagnostic only; it remains a consuming-UI teal/blue treatment and never becomes red in core behavior.\n- Add optional structured MSK2 status payload helpers while preserving legacy payload compatibility.\n- Update README and Fabric embedded reference guidance for mod writers.