refactor(frontend): share formatDatePart between life dates and relationships

formatLifeDate and the relationship formatEnd were the same nullable-date →
formatDocumentDate delegation (YEAR fallback, '' on null). Hoist that core into
formatDatePart in documentDate.ts; formatLifeDate becomes a thin glyph-free
alias and formatRelationshipDateRange calls the shared helper directly. The two
range composers stay separate — they genuinely differ (*/† glyphs vs leading
dash). relationshipDates, personLifeDates and documentDate specs (60) stay green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/person/personLifeDates.ts

@@ -1,23 +1,17 @@
-import { formatDocumentDate, type DatePrecision } from '$lib/shared/utils/documentDate';
+import { formatDatePart, type DatePrecision } from '$lib/shared/utils/documentDate';
 
 /**
- * Formats one life date (birth or death) at the precision the data claims,
+ * Formats one life date (birth or death) at the precision the data claims.
- * delegating all rendering to {@link formatDocumentDate}. Returns '' for a
+ * Thin domain alias over the shared {@link formatDatePart}: carries no * / †
- * missing date. Carries no * / † glyph — components that need the glyphs wrap
+ * glyph — components that need the glyphs wrap them in their own `aria-hidden`
- * them in their own `aria-hidden` markup so screen readers only hear the date.
+ * markup so screen readers only hear the date.
- *
- * A missing precision falls back to YEAR: pre-V76 rows only knew a year, and
- * a bare year is the only safe rendering for a date without precision metadata.
  */
 export function formatLifeDate(
 	date: string | null | undefined,
 	precision: DatePrecision | null | undefined,
 	locale?: string
 ): string {
-	if (!date) {
+	return formatDatePart(date, precision, locale);
-		return '';
-	}
-	return formatDocumentDate(date, precision ?? 'YEAR', null, null, locale);
 }
 
 /**

frontend/src/lib/person/relationshipDates.ts

@@ -1,21 +1,4 @@
-import { formatDocumentDate, type DatePrecision } from '$lib/shared/utils/documentDate';
+import { formatDatePart, type DatePrecision } from '$lib/shared/utils/documentDate';
-
-/**
- * Formats one relationship endpoint (start or end) at the precision the data
- * claims, delegating all rendering to {@link formatDocumentDate}. Returns '' for
- * a missing date. A missing precision falls back to YEAR — pre-V78 rows only knew
- * a year. Mirrors {@link formatLifeDate} for the person life-date pattern.
- */
-function formatEnd(
-	date: string | null | undefined,
-	precision: DatePrecision | null | undefined,
-	locale?: string
-): string {
-	if (!date) {
-		return '';
-	}
-	return formatDocumentDate(date, precision ?? 'YEAR', null, null, locale);
-}
 
 /**
  * Formats a relationship's start–end range as plain text, e.g. for a marriage row.
@@ -32,8 +15,8 @@ export function formatRelationshipDateRange(
 	toDatePrecision: DatePrecision | null | undefined,
 	locale?: string
 ): string {
-	const from = formatEnd(fromDate, fromDatePrecision, locale);
+	const from = formatDatePart(fromDate, fromDatePrecision, locale);
-	const to = formatEnd(toDate, toDatePrecision, locale);
+	const to = formatDatePart(toDate, toDatePrecision, locale);
 	if (from && to) {
 		return `${from} – ${to}`;
 	}

frontend/src/lib/shared/utils/documentDate.ts

@@ -66,6 +66,27 @@ export function formatDocumentDate(
 	}
 }
 
+/**
+ * Formats one nullable date at the precision the data claims, delegating all
+ * rendering to {@link formatDocumentDate}. Returns '' for a missing date; a
+ * missing precision falls back to YEAR — pre-precision rows knew only a year,
+ * and a bare year is the only safe rendering without precision metadata.
+ *
+ * This is the shared core of {@link formatLifeDate} (person birth/death) and the
+ * relationship from/to formatter. Range-level glyphs and dashes belong in those
+ * domain wrappers, never here.
+ */
+export function formatDatePart(
+	date: string | null | undefined,
+	precision: DatePrecision | null | undefined,
+	locale?: string
+): string {
+	if (!date) {
+		return '';
+	}
+	return formatDocumentDate(date, precision ?? 'YEAR', null, null, locale);
+}
+
 // ─── precision branches ──────────────────────────────────────────────────────
 
 function longDate(iso: string, locale: string): string {