docs(person): note YEAR seeding of legacy precisions in ADR-039

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/adr/039-person-life-dates-localdate-precision.md

@@ -45,6 +45,13 @@ are semantically nonsensical for a birth or death, and `APPROX` is excluded from
 form to reduce cognitive load for the senior author audience. Legacy `APPROX` rows
 still render correctly (display delegates to `formatDocumentDate`).
 
+The edit form seeds a stored non-offered precision (`APPROX`/`SEASON`/`RANGE`) into
+the select as `YEAR`, so an untouched save coerces it to `YEAR` ("ca. 1944" becomes
+"1944"). Accepted: nothing currently writes those precisions to persons (the form
+offers DAY/MONTH/YEAR, the importer writes YEAR/UNKNOWN, V76 backfills YEAR), so the
+case is only reachable via direct API writes — and seeding `YEAR` is strictly safer
+than the alternative of silently claiming `DAY` precision.
+
 ### 3. Derived-year pattern for backward-compatible DTOs
 
 `PersonNodeDTO` (Stammbaum) and `RelationshipDTO` keep `Integer birthYear/deathYear`,