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/stores/agents.ts

@@ -11,7 +11,7 @@
 import { defineStore } from 'pinia'
 import { apiFetch } from '../services/api'
 import type { AgentNodeData } from '../composables/useFlowLayout'
-import type { AgentDetail, ThinkingItem } from '../components/dashboard/v2/types'
+import type { AgentDetailData, ThinkingItem } from '../components/dashboard/v2/types'
 
 /* ── API Response Shapes ──────────────────────────── */
 
@@ -127,7 +127,7 @@ function buildThinkingItems(data: AgentNodeData): ThinkingItem[] {
   return items
 }
 
-export function buildAgentDetail(data: AgentNodeData, models: { id: string; alias: string }[]): AgentDetail {
+export function buildAgentDetail(data: AgentNodeData, models: { id: string; alias: string }[]): AgentDetailData {
   const tokenNum = parseFloat(data.tokens?.replace(/[^0-9.]/g, '') || '0')
   const tokenMultiplier = data.tokens?.includes('M') ? 1_000_000 : data.tokens?.includes('k') ? 1_000 : 1
   const tokensToday = Math.round(tokenNum * tokenMultiplier)
@@ -177,7 +177,7 @@ export const useAgentStore = defineStore('agents', {
     },
 
     /** Selected agent detail for modal */
-    selectedAgent(state): AgentDetail | null {
+    selectedAgent(state): AgentDetailData | null {
       if (!state.selectedAgentId) return null
       const data = state.agents.find(a => a.id === state.selectedAgentId)
       if (!data) return null