feat: Vue SPA demo mode support

- useToast.ts: global reactive toast singleton for cross-component toasts
- App.vue: sticky demo mode banner + global toast slot
- router: bypass wizard gate entirely in demo mode (pre-seeded data)
- ApplyWorkspace, CompanyResearchModal: guard generate() in demo mode
- fineTune store: guard submitJob() in demo mode
- ui_switcher.py: remove Vue→Streamlit fallback in demo mode (now handled natively)

All LLM-triggering actions show a toast and no-op in demo mode.
Backend already blocks inference via DEMO_MODE env; Vue layer adds UX signal.

Closes #46

app/components/ui_switcher.py

@@ -124,12 +124,6 @@ def sync_ui_cookie(yaml_path: Path, tier: str) -> None:
         # UI components must not crash the app — silent fallback to default
         pref = "streamlit"
 
-    # Demo mode: Vue SPA has no demo data wiring — always serve Streamlit.
-    # (The tier downgrade check below is skipped in demo mode, but we must
-    # also block the Vue navigation itself so Caddy doesn't route to a blank SPA.)
-    if pref == "vue" and _DEMO_MODE:
-        pref = "streamlit"
-
     # Tier downgrade protection (skip in demo — demo bypasses tier gate)
     if pref == "vue" and not _DEMO_MODE and not can_use(tier, "vue_ui_beta"):
         if profile is not None:

web/src/App.vue

@@ -6,7 +6,20 @@
     <main class="app-main" :class="{ 'app-main--wizard': isWizard }" id="main-content" tabindex="-1">
       <!-- Skip to main content link (screen reader / keyboard nav) -->
       <a href="#main-content" class="skip-link">Skip to main content</a>
+
+      <!-- Demo mode banner — sticky top bar, visible on all pages -->
+      <div v-if="config.isDemo" class="demo-banner" role="status" aria-live="polite">
+        👁 Demo mode — changes are not saved and AI features are disabled.
+      </div>
+
       <RouterView />
+
+      <!-- Global toast — rendered at App level so any component can trigger it -->
+      <Transition name="global-toast">
+        <div v-if="toast.message.value" class="global-toast" role="status" aria-live="polite">
+          {{ toast.message.value }}
+        </div>
+      </Transition>
     </main>
   </div>
 </template>
@@ -17,13 +30,17 @@ import { RouterView, useRoute } from 'vue-router'
 import { useMotion } from './composables/useMotion'
 import { useHackerMode, useKonamiCode } from './composables/useEasterEgg'
 import { useTheme } from './composables/useTheme'
+import { useToast } from './composables/useToast'
 import AppNav from './components/AppNav.vue'
+import { useAppConfigStore } from './stores/appConfig'
 import { useDigestStore } from './stores/digest'
 
 const motion = useMotion()
 const route = useRoute()
 const { toggle, restore } = useHackerMode()
 const { initTheme } = useTheme()
+const toast = useToast()
+const config = useAppConfigStore()
 const digestStore = useDigestStore()
 
 const isWizard = computed(() => route.path.startsWith('/setup'))
@@ -110,4 +127,51 @@ body {
   margin-left: 0;
   padding-bottom: 0;
 }
+
+/* Demo mode banner — sticky top bar */
+.demo-banner {
+  position: sticky;
+  top: 0;
+  z-index: 200;
+  background: var(--color-warning);
+  color: #1a1a1a;  /* forced dark — warning bg is always light enough */
+  text-align: center;
+  font-size: 0.85rem;
+  font-weight: 600;
+  padding: 6px var(--space-4, 16px);
+  letter-spacing: 0.01em;
+}
+
+/* Global toast — bottom-center, above tab bar */
+.global-toast {
+  position: fixed;
+  bottom: calc(72px + env(safe-area-inset-bottom));
+  left: 50%;
+  transform: translateX(-50%);
+  background: var(--color-surface-raised, #2a3650);
+  color: var(--color-text, #eaeff8);
+  padding: 10px 20px;
+  border-radius: var(--radius-md, 8px);
+  font-size: 0.9rem;
+  font-weight: 500;
+  box-shadow: 0 4px 16px rgba(0,0,0,0.25);
+  white-space: nowrap;
+  z-index: 9000;
+  pointer-events: none;
+}
+
+.global-toast-enter-active, .global-toast-leave-active {
+  transition: opacity 220ms ease, transform 220ms ease;
+}
+.global-toast-enter-from, .global-toast-leave-to {
+  opacity: 0;
+  transform: translateX(-50%) translateY(8px);
+}
+
+@media (min-width: 1024px) {
+  .global-toast {
+    bottom: calc(24px + env(safe-area-inset-bottom));
+    left: calc(50% + var(--sidebar-width, 220px) / 2);
+  }
+}
 </style>

web/src/components/ApplyWorkspace.vue

@@ -283,9 +283,12 @@
 <script setup lang="ts">
 import { ref, computed, watch, onMounted, onUnmounted, nextTick } from 'vue'
 import { useApiFetch } from '../composables/useApi'
+import { useAppConfigStore } from '../stores/appConfig'
 import type { Job } from '../stores/review'
 import ResumeOptimizerPanel from './ResumeOptimizerPanel.vue'
 
+const config = useAppConfigStore()
+
 const props = defineProps<{ jobId: number }>()
 
 const emit = defineEmits<{
@@ -379,6 +382,7 @@ async function pollTaskStatus() {
 
 async function generate() {
   if (generating.value) return
+  if (config.isDemo) { showToast('AI features are disabled in demo mode'); return }
   generating.value = true
   clState.value    = 'queued'
   taskError.value  = null

web/src/components/CompanyResearchModal.vue

@@ -88,6 +88,10 @@
 <script setup lang="ts">
 import { ref, onMounted, onUnmounted } from 'vue'
 import { useApiFetch } from '../composables/useApi'
+import { useAppConfigStore } from '../stores/appConfig'
+import { showToast } from '../composables/useToast'
+
+const config = useAppConfigStore()
 
 const props = defineProps<{
   jobId: number
@@ -181,6 +185,7 @@ async function load() {
 }
 
 async function generate() {
+  if (config.isDemo) { showToast('AI features are disabled in demo mode'); state.value = 'empty'; return }
   state.value = 'generating'
   stage.value = null
   errorMsg.value = null

web/src/composables/useToast.ts

@@ -0,0 +1,20 @@
+/**
+ * useToast — global reactive toast singleton.
+ *
+ * Module-level ref shared across all importers; no Pinia needed for a single
+ * ephemeral string. Call showToast() from anywhere; App.vue renders it.
+ */
+import { ref } from 'vue'
+
+const _message = ref<string | null>(null)
+let _timer = 0
+
+export function showToast(msg: string, duration = 3500): void {
+  clearTimeout(_timer)
+  _message.value = msg
+  _timer = window.setTimeout(() => { _message.value = null }, duration)
+}
+
+export function useToast() {
+  return { message: _message }
+}

web/src/router/index.ts

@@ -56,6 +56,9 @@ router.beforeEach(async (to, _from, next) => {
   const config = useAppConfigStore()
   if (!config.loaded) await config.load()
 
+  // Demo mode: pre-seeded data, no wizard needed — route freely
+  if (config.isDemo) return next()
+
   // Wizard gate runs first for every route except /setup itself
   if (!to.path.startsWith('/setup') && !config.wizardComplete) {
     return next('/setup')

web/src/stores/settings/fineTune.ts

@@ -1,6 +1,8 @@
 import { ref } from 'vue'
 import { defineStore } from 'pinia'
 import { useApiFetch } from '../../composables/useApi'
+import { useAppConfigStore } from '../appConfig'
+import { showToast } from '../../composables/useToast'
 
 export interface TrainingPair {
   index: number
@@ -41,6 +43,7 @@ export const useFineTuneStore = defineStore('settings/fineTune', () => {
   }
 
   async function submitJob() {
+    if (useAppConfigStore().isDemo) { showToast('AI features are disabled in demo mode'); return }
     const { data, error } = await useApiFetch<{ job_id: string }>('/api/settings/fine-tune/submit', { method: 'POST' })
     if (!error && data) { inFlightJob.value = true; jobStatus.value = 'queued' }
   }