feat(ai): extensible agent tool registry

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

lib/ai/agent/registry.js

@@ -0,0 +1,17 @@
+export function createRegistry() {
+  const tools = new Map();
+  return {
+    registerTool(def) {
+      if (!def?.name) throw new Error('tool def needs a name');
+      if (tools.has(def.name)) throw new Error(`tool "${def.name}" already registered`);
+      tools.set(def.name, def);
+    },
+    getTool(name) { return tools.get(name); },
+    listTools() { return [...tools.values()]; },
+    // Anthropic tool-use schema — handlers are intentionally stripped.
+    toAnthropicTools() {
+      return [...tools.values()].map(({ name, description, input_schema }) =>
+        ({ name, description, input_schema }));
+    }
+  };
+}