refactor: extract duplicated utility functions into shared modules

Consolidate 20+ duplicate function definitions across UI components into
three shared util files (format-utils, agent-utils, config-draft-utils).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/components/LayoutShell.tsx

@@ -34,6 +34,7 @@ import type { ReactNode } from 'react';
 import { ContentTabs } from './ContentTabs';
 import { EnvironmentSelector } from './EnvironmentSelector';
 import { useScope } from '../hooks/useScope';
+import { formatDuration } from '../utils/format-utils';
 import {
   buildAppTreeNodes,
   buildAdminTreeNodes,
@@ -162,12 +163,6 @@ function healthToSearchColor(health: string): string {
   }
 }
 
-function formatDuration(ms: number): string {
-  if (ms >= 60_000) return `${(ms / 1000).toFixed(0)}s`;
-  if (ms >= 1000) return `${(ms / 1000).toFixed(2)}s`;
-  return `${ms}ms`;
-}
-
 function statusToColor(status: string): string {
   switch (status) {
     case 'COMPLETED': return 'success';