feat: add AgentInstance detail page and improve AgentHealth

- New /agents/:appId/:instanceId page with process info, 3x2 charts
  grid (CPU, memory, throughput, errors, threads, GC), application
  log viewer with level filtering, and instance-scoped timeline
- AgentHealth now uses slide-in DetailPanel for quick instance preview
- Stat strip enhanced: colored StatusDot breakdowns, route ratio with
  state-colored values, Groups renamed to Applications
- Unified page structure: stat strip → scope trail with inline badges
  (removed duplicate section headers from both pages)
- StatCard value/detail props now accept ReactNode
- Log and timeline displayed side by side

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

src/App.tsx

@@ -5,6 +5,7 @@ import { Metrics } from './pages/Metrics/Metrics'
 import { RouteDetail } from './pages/RouteDetail/RouteDetail'
 import { ExchangeDetail } from './pages/ExchangeDetail/ExchangeDetail'
 import { AgentHealth } from './pages/AgentHealth/AgentHealth'
+import { AgentInstance } from './pages/AgentInstance/AgentInstance'
 import { Inventory } from './pages/Inventory/Inventory'
 import { AuditLog } from './pages/Admin/AuditLog/AuditLog'
 import { OidcConfig } from './pages/Admin/OidcConfig/OidcConfig'
@@ -85,6 +86,7 @@ export default function App() {
         <Route path="/metrics" element={<Metrics />} />
         <Route path="/routes/:id" element={<RouteDetail />} />
         <Route path="/exchanges/:id" element={<ExchangeDetail />} />
+        <Route path="/agents/:appId/:instanceId" element={<AgentInstance />} />
         <Route path="/agents/*" element={<AgentHealth />} />
         <Route path="/admin" element={<Navigate to="/admin/rbac" replace />} />
         <Route path="/admin/audit" element={<AuditLog />} />