fix: align AgentInstance page with mock design

- Chart headers: add current value meta text (CPU %, memory MB, TPS,
  error rate, thread count) matching mock layout
- Bottom section: 2-column grid with log placeholder (left) and
  timeline events (right) matching mock layout
- Timeline header: show "Timeline" + event count like mock
- Remove duplicate EmptyState placeholder

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

ui/src/pages/AgentInstance/AgentInstance.module.css

@@ -145,3 +145,31 @@
   color: var(--text-primary);
   margin-bottom: 12px;
 }
+
+.chartMeta {
+  font-size: 11px;
+  font-weight: 500;
+  color: var(--text-muted);
+  font-family: var(--font-mono);
+}
+
+.bottomSection {
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: 14px;
+  margin-bottom: 20px;
+}
+
+.eventCount {
+  font-size: 11px;
+  font-weight: 500;
+  color: var(--text-muted);
+  font-family: var(--font-mono);
+}
+
+.emptyEvents {
+  padding: 20px;
+  text-align: center;
+  font-size: 12px;
+  color: var(--text-muted);
+}

ui/src/pages/AgentInstance/AgentInstance.tsx

@@ -200,54 +200,76 @@ export default function AgentInstance() {
         </>
       )}
 
-      <div className={styles.sectionTitle}>Performance</div>
       <div className={styles.chartsGrid}>
         <div className={styles.chartCard}>
-          <div className={styles.chartHeader}><div className={styles.chartTitle}>CPU Usage</div></div>
+          <div className={styles.chartHeader}>
+            <div className={styles.chartTitle}>CPU Usage</div>
+            <div className={styles.chartMeta}>{cpuPct != null ? `${(cpuPct * 100).toFixed(0)}% current` : ''}</div>
+          </div>
           {cpuSeries
             ? <AreaChart series={cpuSeries} yLabel="%" height={200} />
             : <EmptyState title="No data" description="No CPU metrics available" />}
         </div>
         <div className={styles.chartCard}>
-          <div className={styles.chartHeader}><div className={styles.chartTitle}>Memory Heap</div></div>
+          <div className={styles.chartHeader}>
+            <div className={styles.chartTitle}>Memory (Heap)</div>
+            <div className={styles.chartMeta}>{heapUsed != null && heapMax != null ? `${(heapUsed / (1024 * 1024)).toFixed(0)} MB / ${(heapMax / (1024 * 1024)).toFixed(0)} MB` : ''}</div>
+          </div>
           {heapSeries
             ? <AreaChart series={heapSeries} yLabel="MB" height={200} />
             : <EmptyState title="No data" description="No heap metrics available" />}
         </div>
         <div className={styles.chartCard}>
-          <div className={styles.chartHeader}><div className={styles.chartTitle}>Throughput</div></div>
+          <div className={styles.chartHeader}>
+            <div className={styles.chartTitle}>Throughput</div>
+            <div className={styles.chartMeta}>{agent?.tps != null ? `${agent.tps.toFixed(1)} msg/s` : ''}</div>
+          </div>
           {throughputSeries
-            ? <AreaChart series={throughputSeries} height={200} />
+            ? <AreaChart series={throughputSeries} yLabel="msg/s" height={200} />
             : <EmptyState title="No data" description="No throughput data in range" />}
         </div>
         <div className={styles.chartCard}>
-          <div className={styles.chartHeader}><div className={styles.chartTitle}>Error Rate</div></div>
+          <div className={styles.chartHeader}>
+            <div className={styles.chartTitle}>Error Rate</div>
+            <div className={styles.chartMeta}>{agent?.errorRate != null ? `${(agent.errorRate * 100).toFixed(1)}%` : ''}</div>
+          </div>
           {errorSeries
-            ? <LineChart series={errorSeries} height={200} />
+            ? <LineChart series={errorSeries} yLabel="%" height={200} />
             : <EmptyState title="No data" description="No error data in range" />}
         </div>
         <div className={styles.chartCard}>
-          <div className={styles.chartHeader}><div className={styles.chartTitle}>Thread Count</div></div>
+          <div className={styles.chartHeader}>
+            <div className={styles.chartTitle}>Thread Count</div>
+            {threadSeries && <div className={styles.chartMeta}>{threadSeries[0].data[threadSeries[0].data.length - 1]?.y.toFixed(0)} active</div>}
+          </div>
           {threadSeries
-            ? <LineChart series={threadSeries} height={200} />
+            ? <LineChart series={threadSeries} yLabel="threads" height={200} />
             : <EmptyState title="No data" description="No thread metrics available" />}
         </div>
         <div className={styles.chartCard}>
-          <div className={styles.chartHeader}><div className={styles.chartTitle}>GC Pauses</div></div>
+          <div className={styles.chartHeader}>
+            <div className={styles.chartTitle}>GC Pauses</div>
+          </div>
           {gcSeries
             ? <BarChart series={gcSeries} yLabel="ms" height={200} />
             : <EmptyState title="No data" description="No GC metrics available" />}
         </div>
       </div>
 
-      {feedEvents.length > 0 && (
-        <div className={styles.eventCard}>
-          <div className={styles.eventCardHeader}>Events</div>
-          <EventFeed events={feedEvents} maxItems={50} />
-        </div>
-      )}
+      <div className={styles.bottomSection}>
+        <EmptyState title="Application Log" description="Application log streaming is not yet available" />
+
+        <div className={styles.eventCard}>
+          <div className={styles.eventCardHeader}>
+            <span>Timeline</span>
+            <span className={styles.eventCount}>{feedEvents.length} events</span>
+          </div>
+          {feedEvents.length > 0
+            ? <EventFeed events={feedEvents} maxItems={50} />
+            : <div className={styles.emptyEvents}>No events in the selected time range.</div>}
+        </div>
+      </div>
 
-      <EmptyState title="Application Logs" description="Application log streaming is not yet available" />
     </div>
   );
 }