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/dashboard/v2/TaskStrip.vue

@@ -10,11 +10,29 @@ import type { TaskItem } from './types'
 
 defineProps<{
   tasks: TaskItem[]
+  loading?: boolean
+  error?: string | null
 }>()
 </script>
 
 <template>
   <div class="taskstrip v2-scroll">
+    <!-- Loading skeleton -->
+    <template v-if="loading">
+      <div v-for="n in 3" :key="'sk-' + n" class="taskcard skeleton" />
+    </template>
+
+    <!-- Error -->
+    <div v-else-if="error" class="task-error">
+      <span class="error-icon">⚠</span> {{ error }}
+    </div>
+
+    <!-- Empty -->
+    <div v-else-if="!tasks.length" class="task-empty">
+      No active tasks
+    </div>
+
+    <!-- Tasks -->
     <div
       v-for="task in tasks"
       :key="task.id"
@@ -169,4 +187,40 @@ defineProps<{
   background: var(--st-block);
   opacity: 0.55;
 }
+
+/* ── Skeleton ─────────────────────────────────── */
+.taskcard.skeleton {
+  height: 98px;
+  background: var(--glass);
+  animation: skeleton-pulse 1.5s ease-in-out infinite;
+}
+
+@keyframes skeleton-pulse {
+  0%, 100% { opacity: 0.5; }
+  50%      { opacity: 0.8; }
+}
+
+/* ── Error ────────────────────────────────────── */
+.task-error {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  font-family: 'Manrope', sans-serif;
+  font-size: 11px;
+  color: #fda4b0;
+  padding: 12px;
+  white-space: nowrap;
+}
+
+.error-icon { flex: 0 0 auto; font-size: 14px; }
+
+/* ── Empty ────────────────────────────────────── */
+.task-empty {
+  font-family: 'Manrope', sans-serif;
+  font-size: 11px;
+  color: var(--tx-3);
+  font-style: italic;
+  padding: 12px;
+  white-space: nowrap;
+}
 </style>