Locales: Vietnamese for the setback-too-short refusal, now that vi is a complete catalog

Main made vi a complete catalog; develop's new message (ui.fillet_error_setback_short) had no vi
entry, so every_complete_catalog_carries_every_english_message failed on the merged tree.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DtL5M41G8Nua7HvuFPZkmJ

assets/locales/pending/fillet-setback-at-least.json

@@ -19,5 +19,8 @@
   },
   "zh": {
     "ui.fillet_error_setback_short": "对于此角点的面片，后退距离太短：从 {least} 起可以构建。请尝试更长的后退距离。"
+  },
+  "vi": {
+    "ui.fillet_error_setback_short": "Khoảng lùi quá ngắn cho mảng ở góc này: góc dựng được từ {least} trở lên. Hãy thử một khoảng Lùi dài hơn."
   }
 }