feat: wire up agents and expose via opencode plugin

src/agents/index.ts

@@ -0,0 +1,10 @@
+import type { AgentConfig } from "@opencode-ai/sdk"
+import { oracleAgent } from "./oracle"
+import { librarianAgent } from "./librarian"
+import { exploreAgent } from "./explore"
+
+export const builtinAgents: Record<string, AgentConfig> = {
+  oracle: oracleAgent,
+  librarian: librarianAgent,
+  explore: exploreAgent,
+}