fix(web): LabelEditor preserves other-language labels on edit (#55)

Editing a term/authority/field that already had labels in other languages
silently replaced the whole multilingual set with one default-language entry.
onChange now keeps non-default-language entries; the editor shows only the
default-language label (no longer falling back to an other-language one, which
made the clear/edit path write the wrong language) and surfaces a hint when
other-language labels exist on the record.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/components/label-editor.tsx

@@ -7,9 +7,10 @@ import { Label } from "@/components/ui/label";
 
 type LabelInput = components["schemas"]["LabelInput"];
 
-/** Single-language label editor. Authors one label at the instance default language;
- *  emits a one-entry LabelInput[] (empty array when blank). The multilingual data model
- *  is unchanged — this only simplifies authoring. */
+/** Single-language label editor. Authors one label at the instance default language.
+ *  Editing only touches the default-language entry — labels in other languages on the
+ *  same record are preserved (not collapsed), so editing a term/authority that already
+ *  has e.g. an English label keeps it. */
 export function LabelEditor({
   value,
   onChange,
@@ -20,16 +21,22 @@ export function LabelEditor({
   const { t } = useTranslation();
   const { default_language } = useConfig();
 
-  const current =
-    value.find((l) => l.lang === default_language)?.label ?? value[0]?.label ?? "";
+  const current = value.find((l) => l.lang === default_language)?.label ?? "";
+  const hasOtherLanguages = value.some((l) => l.lang !== default_language);
 
   const set = (label: string) =>
-    onChange(label.trim() ? [{ lang: default_language, label }] : []);
+    onChange([
+      ...value.filter((l) => l.lang !== default_language),
+      ...(label.trim() ? [{ lang: default_language, label }] : []),
+    ]);
 
   return (
     <div className="space-y-1">
       <Label htmlFor="label">{t("labels.label")}</Label>
       <Input id="label" value={current} onChange={(e) => set(e.target.value)} />
+      {hasOtherLanguages && (
+        <p className="text-xs text-muted-foreground">{t("labels.otherLanguages")}</p>
+      )}
     </div>
   );
 }