fix: make workspace export runtime-safe

packages/agent-runtime/index.d.ts

@@ -0,0 +1 @@
+export declare const AGENT_RUNTIME_PACKAGE = "agent-runtime";

packages/agent-runtime/index.js

@@ -0,0 +1 @@
+export const AGENT_RUNTIME_PACKAGE = "agent-runtime";

packages/agent-runtime/package.json

@@ -4,6 +4,9 @@
   "private": true,
   "type": "module",
   "exports": {
-    ".": "./src/index.ts"
+    ".": {
+      "types": "./index.d.ts",
+      "default": "./index.js"
+    }
   }
 }