fix: say "1 email selected" in the tag picker header

locales/rn/de.json

@@ -273,6 +273,7 @@
   },
   "context_menu": {
     "color_tag": "Label",
+    "emails_selected": "{count, plural, one {# E-Mail ausgewählt} other {# E-Mails ausgewählt}}",
     "remove_color": "Label entfernen",
     "rules": {
       "login_changed": "Sie haben das Konto gewechselt, daher wurde die Regel nicht gespeichert"

locales/rn/en.json

@@ -317,6 +317,7 @@
   },
   "context_menu": {
     "color_tag": "Tag",
+    "emails_selected": "{count, plural, one {# email selected} other {# emails selected}}",
     "remove_color": "Remove tag",
     "rules": {
       "login_changed": "You switched accounts, so the rule was not saved"

src/components/TagSheet.tsx

@@ -87,7 +87,9 @@ export function TagSheet({ visible, onClose, keywords, selectedEmails, onToggle
           </View>
           <View style={styles.header}>
             <Text style={styles.title}>
-              {t('context_menu.items_selected', `${selectedEmails.length} emails selected`, { count: selectedEmails.length })}
+              {/* Not context_menu.items_selected: "{count} emails selected" has no
+                  singular, and the sheet opens for one email too. */}
+              {t('context_menu.emails_selected', '{count, plural, one {# email selected} other {# emails selected}}', { count: selectedEmails.length })}
             </Text>
             <Pressable onPress={onClose} hitSlop={10} style={styles.close}
               accessibilityRole="button"

src/components/__tests__/tag-sheet-title.test.ts

@@ -0,0 +1,24 @@
+// The tag picker's header read "1 emails selected": it used the webmail's
+// context_menu.items_selected ("{count} emails selected"), which has no
+// singular since the webmail shows it for several emails only.
+import { describe, expect, it, vi } from 'vitest';
+import fs from 'node:fs';
+import path from 'node:path';
+
+vi.mock('expo-localization', () => ({ getLocales: () => [] }));
+
+import { translate } from '../../i18n';
+
+const source = fs.readFileSync(path.resolve(__dirname, '../TagSheet.tsx'), 'utf8');
+// The key and, when it is a literal, the English fallback.
+const call = /t\('(context_menu\.[a-z_]+)', (?:'([^']*)'|`[^`]*`), \{ count: selectedEmails\.length \}\)/.exec(source);
+
+describe('the tag picker header', () => {
+  it('counts the selection with a plural', () => {
+    expect(call).not.toBeNull();
+    const [, key, fallback] = call!;
+    expect(translate('en', key, fallback, { count: 1 })).toBe('1 email selected');
+    expect(translate('en', key, fallback, { count: 3 })).toBe('3 emails selected');
+    expect(translate('de', key, fallback, { count: 1 })).toBe('1 E-Mail ausgewählt');
+  });
+});