feat(ui): clean demo URL + 'Back to landing' in banner

ui/src/api.ts

@@ -80,8 +80,16 @@ const DEMO = (() => {
   if (typeof window === 'undefined') return ENV.VITE_DEMO === '1'
   try {
     const q = new URLSearchParams(window.location.search)
-    if (q.get('demo') === '1') { localStorage.setItem('konclave.demo', '1'); return true }
-    if (q.get('demo') === '0') { localStorage.removeItem('konclave.demo'); return false }
+    const flag = q.get('demo')
+    if (flag === '1' || flag === '0') {
+      if (flag === '1') localStorage.setItem('konclave.demo', '1')
+      else localStorage.removeItem('konclave.demo')
+      // Strip `?demo` from the address bar so the path stays clean; the mode persists via localStorage.
+      q.delete('demo')
+      const qs = q.toString()
+      window.history.replaceState(null, '', window.location.pathname + (qs ? `?${qs}` : '') + window.location.hash)
+      return flag === '1'
+    }
     if (localStorage.getItem('konclave.demo') === '1') return true
   } catch { /* storage unavailable — fall through to the build flag */ }
   return ENV.VITE_DEMO === '1'

ui/src/components.tsx

@@ -3,20 +3,19 @@ import { Link } from 'react-router-dom'
 import { useReveal } from './reveal'
 import { useI18n, useT } from './i18n'
 import { IS_DEMO } from './api'
-import { helperConfigured } from './helper'
 
 /** A thin, always-visible strip in demo mode (runtime `?demo=1` or the VITE_DEMO fallback) so a
- *  visitor never mistakes the sample data for a real vault. Offers "Exit demo" (`?demo=0`) ONLY when
- *  a real mode exists to exit to (a helper is configured) — a pure demo deploy has nowhere to go, so
- *  the exit would land on an empty backend. Renders nothing outside demo mode. */
+ *  visitor never mistakes the sample data for a real vault. Always offers a way back to the landing
+ *  (which leaves demo mode via `?demo=0`), from where a visitor re-enters the demo or the real vault.
+ *  Renders nothing outside demo mode. */
 export function DemoBanner() {
   const t = useT()
   if (!IS_DEMO) return null
   return (
     <div className="demo-banner" role="note">
       <span className="demo-banner-tag">DEMO</span>
       {t('demo.bannerNote')}
-      {helperConfigured() && <a className="demo-banner-exit" href="?demo=0">{t('demo.bannerExit')}</a>}
+      <a className="demo-banner-exit" href="?demo=0">{t('demo.bannerExit')}</a>
     </div>
   )
 }

ui/src/i18n/en.ts

@@ -234,7 +234,7 @@ export const en: Record<string, string> = {
   'demo.live': 'Live demo',
   'demo.note': 'This is the cryptography itself, running live, not the everyday vault screens.',
   'demo.bannerNote': 'Demonstration with sample data. No real funds, no real transactions.',
-  'demo.bannerExit': 'Exit demo',
+  'demo.bannerExit': '← Back to landing',
   'settings.eyebrow': 'SETTINGS',
   'settings.title': 'Settings',
   'settings.vault': 'Vault',

ui/src/i18n/pt-BR.ts

@@ -234,7 +234,7 @@ export const ptBR: Record<string, string> = {
   'demo.live': 'Demonstração ao vivo',
   'demo.note': 'Isto é a própria criptografia, rodando ao vivo, não as telas do dia a dia do cofre.',
   'demo.bannerNote': 'Demonstração com dados de exemplo. Nenhum fundo real, nenhuma transação de verdade.',
-  'demo.bannerExit': 'Sair da demo',
+  'demo.bannerExit': '← Voltar à landing',
   'settings.eyebrow': 'AJUSTES',
   'settings.title': 'Ajustes',
   'settings.vault': 'Cofre',