Fix streaming for z-ai in anthropic provider, add preliminary support for tool call streaming. Only reporting argument string deltas, not partial JSON objects

packages/ai/src/index.ts

@@ -1,3 +1,4 @@
+export * from "./agent/index.js";
 export * from "./generate.js";
 export * from "./models.js";
 export * from "./providers/anthropic.js";