feat: add zCode Swarm — multi-agent orchestration system

- 6 agent skills: code-review, performance, security, architecture, test, git
- 4 coordinator modes: hierarchical, mesh, gossip, consensus
- Federated memory system (6 namespaces)
- Neural network agent recommendation
- Agent marketplace (plugin discovery/install)
- Real-time dashboard + performance metrics
- CRDT-based sync for decentralized modes
- 22 files, ~1400 lines total

Inspired by ruflo distributed multi-agent patterns.

.zcode/lib/performance-metrics.cjs

@@ -0,0 +1,76 @@
+/**
+ * Performance Metrics Collector
+ * Real-time system and swarm performance monitoring
+ */
+
+class PerformanceMetricsCollector {
+  constructor(swarm) {
+    this.swarm = swarm;
+    this.metrics = [];
+    this.collectionInterval = null;
+    this.maxSamples = 100;
+  }
+
+  startCollection(intervalMs = 60000) {
+    this.collectionInterval = setInterval(() => {
+      this.collect();
+    }, intervalMs);
+    this.swarm.log('success', 'Performance metrics collection started');
+  }
+
+  stopCollection() {
+    if (this.collectionInterval) {
+      clearInterval(this.collectionInterval);
+      this.collectionInterval = null;
+    }
+  }
+
+  collect() {
+    const sample = {
+      timestamp: Date.now(),
+      memory: process.memoryUsage(),
+      cpu: process.cpuUsage(),
+      uptime: process.uptime(),
+      agents: this.swarm.getPerformanceReport?.()?.agents || {}
+    };
+    this.metrics.push(sample);
+    if (this.metrics.length > this.maxSamples) {
+      this.metrics.shift();
+    }
+  }
+
+  getReport() {
+    if (this.metrics.length === 0) return { status: 'no_data' };
+
+    const latest = this.metrics[this.metrics.length - 1];
+    const previous = this.metrics.length > 1 ? this.metrics[this.metrics.length - 2] : latest;
+
+    const memDiff = latest.memory.heapUsed - previous.memory.heapUsed;
+    const trend = memDiff > 1000000 ? 'increasing' : memDiff < -1000000 ? 'decreasing' : 'stable';
+
+    return {
+      current: {
+        heapUsed: `${(latest.memory.heapUsed / 1024 / 1024).toFixed(1)}MB`,
+        heapTotal: `${(latest.memory.heapTotal / 1024 / 1024).toFixed(1)}MB`,
+        rss: `${(latest.memory.rss / 1024 / 1024).toFixed(1)}MB`,
+        uptime: `${Math.floor(latest.uptime)}s`,
+        cpuUser: `${(latest.cpu.user / 1000000).toFixed(1)}s`,
+        cpuSystem: `${(latest.cpu.system / 1000000).toFixed(1)}s`
+      },
+      trend,
+      samples: this.metrics.length,
+      recommendations: this.generateRecommendations(latest)
+    };
+  }
+
+  generateRecommendations(sample) {
+    const recs = [];
+    const heapMB = sample.memory.heapUsed / 1024 / 1024;
+    if (heapMB > 400) recs.push('⚠️ High memory usage — consider restarting');
+    if (sample.uptime > 86400) recs.push('🔄 Long uptime — scheduled restart recommended');
+    if (recs.length === 0) recs.push('✅ System performance within normal range');
+    return recs;
+  }
+}
+
+module.exports = PerformanceMetricsCollector;