feat(ai): extensible agent tool registry

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/ai/agent/registry.test.js

@@ -0,0 +1,32 @@
+import { describe, it, expect } from 'vitest';
+import { createRegistry } from '../../../lib/ai/agent/registry.js';
+
+describe('tool registry', () => {
+  const def = {
+    name: 'echo',
+    description: 'echo back',
+    input_schema: { type: 'object', properties: { x: { type: 'string' } }, required: ['x'] },
+    handler: async ({ x }) => ({ ok: true, x })
+  };
+
+  it('registers and retrieves a tool', () => {
+    const r = createRegistry();
+    r.registerTool(def);
+    expect(r.getTool('echo')).toBe(def);
+    expect(r.listTools().map(t => t.name)).toEqual(['echo']);
+  });
+
+  it('rejects duplicate names', () => {
+    const r = createRegistry();
+    r.registerTool(def);
+    expect(() => r.registerTool(def)).toThrow(/already registered/);
+  });
+
+  it('serialises to the Anthropic tools shape (no handler leak)', () => {
+    const r = createRegistry();
+    r.registerTool(def);
+    expect(r.toAnthropicTools()).toEqual([
+      { name: 'echo', description: 'echo back', input_schema: def.input_schema }
+    ]);
+  });
+});