candor-swift 0.16.0

The callgraph-aware baseline guard (spec 0.16): a formerly-pure function that turns effectful is caught as a gain (keyed on the baseline callgraph sidecar), rather than exempt as "new code". The ratchet fires only on a real boundary-effect gain; an Unknown-only gain is disclosed as advisory (validated by a real-world corpus test). Floor now 0.16, conformance-pinned four-way.