Preserve year-only Date Issued values

[ewlarson]

Summary

• preserve four-digit Date Issued values as year-only displays
• continue formatting full yyyy-mm-dd values with month and day
• add regression coverage for both year-only and full-date values

Root cause

The Full Details formatter passed year-only strings to JavaScript's generic Date parser. Values such as 1950 were interpreted as January 1, 1950, adding month and day precision that was not present in the record.

Impact

Records containing only a year now display that exact year. Records containing full dates retain the existing readable full-date format.

Validation

• npm test -- --run src/__tests__/components/resource/FullDetailsTable.test.tsx
• ESLint on the changed component and test
• Prettier check on the changed component and test
• npm run build

Closes #237