Merge a default (English) chrome record with a locale-override record, per field. Used by the
build/dev pipeline that emits COMPLETE per-locale packs (English filled where untranslated —
I18N-DESIGN.md decision #1), NOT at runtime: the runtime seeds one already-complete pack, no merge.
A locale override typically carries only label/desc/group, so unspecified fields fall through
to the default; group is merged per groupKey.
Merge a default (English) chrome record with a locale-override record, per field. Used by the build/dev pipeline that emits COMPLETE per-locale packs (English filled where untranslated — I18N-DESIGN.md decision #1), NOT at runtime: the runtime seeds one already-complete pack, no merge. A locale override typically carries only
label/desc/group, so unspecified fields fall through to the default;groupis merged per groupKey.