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/agents/marketplace.cjs

@@ -0,0 +1,76 @@
+/**
+ * Agent Marketplace
+ * Plugin-based agent discovery and installation
+ */
+
+const fs = require('fs');
+const path = require('path');
+
+class AgentMarketplace {
+  constructor() {
+    this.marketplacePath = path.join(__dirname, '../../marketplace');
+    this.installedPath = path.join(__dirname, '../../installed');
+    this.agents = new Map();
+    this.installedAgents = new Map();
+  }
+
+  initialize() {
+    if (!fs.existsSync(this.marketplacePath)) fs.mkdirSync(this.marketplacePath, { recursive: true });
+    if (!fs.existsSync(this.installedPath)) fs.mkdirSync(this.installedPath, { recursive: true });
+    this.loadAgents();
+    this.swarm?.log?.('success', `Marketplace initialized: ${this.agents.size} available`);
+  }
+
+  loadAgents() {
+    try {
+      const files = fs.readdirSync(this.marketplacePath).filter(f => f.endsWith('.json'));
+      for (const file of files) {
+        const data = JSON.parse(fs.readFileSync(path.join(this.marketplacePath, file), 'utf8'));
+        this.agents.set(data.id, data);
+      }
+    } catch {}
+  }
+
+  search(query = '', capabilities = []) {
+    let results = Array.from(this.agents.values());
+    if (query) {
+      results = results.filter(a =>
+        a.name.toLowerCase().includes(query.toLowerCase()) ||
+        a.description.toLowerCase().includes(query.toLowerCase())
+      );
+    }
+    if (capabilities.length) {
+      results = results.filter(a => capabilities.some(c => a.capabilities?.includes(c)));
+    }
+    return results;
+  }
+
+  installAgent(agentId) {
+    const agent = this.agents.get(agentId);
+    if (!agent) throw new Error(`Agent not found: ${agentId}`);
+    if (this.installedAgents.has(agentId)) throw new Error(`Already installed: ${agentId}`);
+
+    const installDir = path.join(this.installedPath, agentId);
+    fs.mkdirSync(installDir, { recursive: true });
+
+    this.installedAgents.set(agentId, { ...agent, installedAt: Date.now() });
+    fs.writeFileSync(
+      path.join(this.installedPath, 'installed.json'),
+      JSON.stringify(Object.fromEntries(this.installedAgents), null, 2)
+    );
+    return { ...agent, installedAt: Date.now() };
+  }
+
+  uninstallAgent(agentId) {
+    if (!this.installedAgents.has(agentId)) throw new Error(`Not installed: ${agentId}`);
+    const dir = path.join(this.installedPath, agentId);
+    if (fs.existsSync(dir)) fs.rmSync(dir, { recursive: true, force: true });
+    this.installedAgents.delete(agentId);
+  }
+
+  listAvailable() { return Array.from(this.agents.values()); }
+  listInstalled() { return Array.from(this.installedAgents.values()); }
+  isInstalled(agentId) { return this.installedAgents.has(agentId); }
+}
+
+module.exports = AgentMarketplace;