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/pages/AgentHealth/AgentHealth.tsx

@@ -316,20 +316,15 @@ export function AgentHealth() {
           />
         </div>
 
-        {/* Scope breadcrumb trail */}
-        {scope.level !== 'all' && (
-          <div className={styles.scopeTrail}>
-            <Link to="/agents" className={styles.scopeLink}>All Agents</Link>
-            <span className={styles.scopeSep}>&#9656;</span>
-            <span className={styles.scopeCurrent}>{scope.appId}</span>
-          </div>
-        )}
-
-        {/* Section header */}
-        <div className={styles.sectionHeaderRow}>
-          <span className={styles.sectionTitle}>
-            {scope.level === 'all' ? 'Agents' : scope.appId}
-          </span>
+        {/* Scope trail + badges */}
+        <div className={styles.scopeTrail}>
+          {scope.level !== 'all' && (
+            <>
+              <Link to="/agents" className={styles.scopeLink}>All Agents</Link>
+              <span className={styles.scopeSep}>&#9656;</span>
+              <span className={styles.scopeCurrent}>{scope.appId}</span>
+            </>
+          )}
           <Badge
             label={`${liveCount}/${totalInstances} live`}
             color={deadCount > 0 ? 'error' : staleCount > 0 ? 'warning' : 'success'}