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/Topbar.vue

@@ -138,9 +138,4 @@ defineProps<{
   height: 15px;
 }
 
-@keyframes pulse-work {
-  0%   { box-shadow: 0 0 0 0   rgba(61,220,151,.55); }
-  70%  { box-shadow: 0 0 0 7px rgba(61,220,151,0); }
-  100% { box-shadow: 0 0 0 0   rgba(61,220,151,0); }
-}
 </style>