refactor(frontend): deduplicate CSS keyframes, unify types, extract format utils, add UI states, trim mock data

- Remove duplicate @keyframes pulse-* from 3 component files (already in nexus-tokens.css)
- Rename AgentDetail → AgentDetailData in dashboard types to avoid collision with types/agent.ts
- Extract shared formatNumber/initials/formatTime to utils/format.ts
- Simplify FlowBoard: use agentStore modal/selection getters instead of duplicating local state
- Add error banner + empty state to IrisChat; add loading skeleton + error/empty states to TaskStrip
- Remove 105-line unused mockAgents array from useFlowLayout
- Reduce operations store fallbacks from hardcoded preview data to minimal safe defaults
- Update operations store tests to match lean fallback structure
- Net: -73 lines, cleaner imports, fewer magic strings

frontend/src/components/layout/AppSidebar.vue

@@ -8,6 +8,7 @@ import {
 } from '@lucide/vue'
 import { useRouter } from 'vue-router'
 import { useAuthStore } from '../../stores/auth'
+import { initials } from '../../utils/format'
 
 const props = defineProps<{
   activeView: string
@@ -23,7 +24,9 @@ const emit = defineEmits<{
 const auth = useAuthStore()
 const router = useRouter()
 
-const ownerInitials = computed(() => auth.user?.displayName.split(' ').map(part => part[0]).join('').slice(0, 2).toUpperCase() ?? 'OW')
+const ownerInitials = computed(() =>
+  auth.user?.displayName ? initials(auth.user.displayName) : 'OW'
+)
 
 const navigation = [
   { label: 'Dashboard', icon: LayoutDashboard },