Adds formatDocumentDate — a pure, branch-per-precision label function that
renders a document date at exactly the precision the data claims (DAY → full
date, MONTH → "Juni 1916", SEASON → localized season word, YEAR → "1916",
APPROX → "ca. 1916", RANGE with collapse/expand/open-ended, UNKNOWN → "Datum
unbekannt"). Delegates to the existing date.ts helpers (shared T12:00:00
convention) and routes every localized word through Paraglide.
A shared docs/date-label-fixtures.json table is asserted by this spec and will
be asserted by the Java title formatter, as the drift guard requested in
review (Markus/Sara). Adds de/en/es precision/season/edit-form i18n keys.
Assumption: SEASON structured label is localized per locale (Decision 4),
with the verbatim raw cell preserved as a separate secondary line by callers.
Refs #666
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
