fix(localizeText): accept { en: "" } as a valid translation (plan 61 S-E)

localizeText({ en: "" }) previously threw "textItems must have an
english translation" because `!textItem.en` is falsy for an empty
string. An empty string IS a valid translation (the author chose "no
text" for that locale); only a genuinely missing `en` should throw.

Switch the guard from `!textItem.en` to `textItem.en == null` so that:
- null / undefined still throw (unchanged contract)
- empty strings return as-is
- empty strings in non-`en` locales fall through to the next preference
  via `!= null` check (was falsy check, which dropped empty strings)

New regression test [LOLY] pins the behaviour. The textItem with consent:
{ en: "" } shape that the Chat preset writes was poisoning peekInvite in
hds-webapp; the safeLocalize wrapper there can now be simplified.

Author: perki

tests/localizeText.test.js

@@ -122,5 +122,17 @@ describe('[LOCX] Localization', () => {
         assert.equal(e.message, 'textItems must have an english translation');
       }
     });
+
+    it('[LOLY] empty string `en` is a valid translation (author chose "no text")', () => {
+      // Regression for S-2026-05-26-E: previously `!textItem.en` swallowed
+      // empty strings and threw "textItems must have an english translation",
+      // breaking invite peeks against Chat presets that wrote `consent: { en: "" }`.
+      assert.equal(localizeText({ en: '' }), '');
+      // Less-preferred locale set to `""` should also fall through to en.
+      setPreferredLocales(['fr']);
+      assert.equal(localizeText({ en: 'Hello', fr: '' }), '');
+      assert.equal(localizeText({ en: 'Hello', fr: null }), 'Hello');
+      assert.equal(localizeText({ en: 'Hello', fr: undefined }), 'Hello');
+    });
   });
 });

ts/localizeText.ts

@@ -37,12 +37,18 @@ export function resetPreferredLocales (): void {
 
 /**
  * return the translation of this item considering the setting of preffered language
+ *
+ * Empty strings `""` are valid translations (the author chose "no text"); the
+ * function returns them as-is and falls through to less-preferred locales only
+ * when a translation is genuinely `null`/`undefined`. Only a missing `en` key
+ * throws.
  */
 export function localizeText (textItem: localizableText | null): string | null {
   if (textItem == null) return null;
-  if (!textItem.en) throw new HDSLibError('textItems must have an english translation', { textItem });
+  if (textItem.en == null) throw new HDSLibError('textItems must have an english translation', { textItem });
   for (const l of preferredLocales) {
-    if (textItem[l as keyof localizableText]) return textItem[l as keyof localizableText];
+    const v = textItem[l as keyof localizableText];
+    if (v != null) return v;
   }
   return textItem.en;
 }