Fix UE launch permission, move it to context menu, refresh History after Submit

- Launch now goes through a backend launch_file command (shell `start`), so
  it works for any path — fixes "Not allowed to open path" from the opener
  plugin's scoped open-path.
- Removed the toolbar Launch-Unreal button; it's now a right-click item on the
  Working folder ("Launch Unreal Engine"), shown only when a .uproject exists.
- Reload History after a successful Submit so the new changelist shows without
  a manual F5.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/i18n.ts

@@ -68,6 +68,7 @@ const D: Record<string, Tr> = {
   "Working…": { ru: "Работаю…", de: "Arbeite…", fr: "En cours…", es: "Trabajando…" },
   "pull from server": { ru: "забрать с сервера (pull)", de: "vom Server holen (pull)", fr: "récupérer du serveur (pull)", es: "traer del servidor (pull)" },
   "Launch": { ru: "Запустить", de: "Starten", fr: "Lancer", es: "Iniciar" },
+  "Launch Unreal Engine": { ru: "Запустить Unreal Engine", de: "Unreal Engine starten", fr: "Lancer Unreal Engine", es: "Iniciar Unreal Engine" },
   "Open this project in Unreal Engine": { ru: "Открыть проект в Unreal Engine", de: "Projekt in Unreal Engine öffnen", fr: "Ouvrir le projet dans Unreal Engine", es: "Abrir el proyecto en Unreal Engine" },
   "Launching Unreal…": { ru: "Запуск Unreal…", de: "Unreal wird gestartet…", fr: "Lancement d’Unreal…", es: "Iniciando Unreal…" },