Reuse the shared offset-instant owner for calendar validation and exact probe ordering. Preserve first-century years, arbitrary recorded fraction digits in the supported offset profile, ordinal ties and legacy native-Date fallback. Keep original clock spelling when conversion leaves the supported four-digit year range, and refuse unrepresentable generated clocks before committing state.
Validation: focused clock/comparison and public CLI regressions cover leap years, offset equivalence, precise DELETE/GET order, spelling classification and refusal atomicity. Replay/state compatibility checks pass. Numeric state intervals and generated-clock progression retain their documented millisecond limits.
Fixes#6835Fixes#6643