Replace Zod with TypeBox for schema validation

- Switch from Zod to TypeBox for tool parameter schemas
- TypeBox schemas can be serialized/deserialized as JSON
- Use AJV for runtime validation instead of Zod's parse
- Add StringEnum helper for Google API compatibility (avoids anyOf/const patterns)
- Export Type and Static from main package for convenience
- Update all tests and documentation to reflect TypeBox usage

packages/ai/test/enum-test.ts

@@ -0,0 +1,17 @@
+import { Type } from "@sinclair/typebox";
+import { z } from "zod";
+import { zodToJsonSchema } from "zod-to-json-schema";
+import { StringEnum } from "../src/typebox-helpers.js";
+
+// Zod version
+const zodSchema = z.object({
+	operation: z.enum(["add", "subtract", "multiply", "divide"]),
+});
+
+// TypeBox with our StringEnum helper
+const typeboxHelper = Type.Object({
+	operation: StringEnum(["add", "subtract", "multiply", "divide"]),
+});
+
+console.log("Zod:", JSON.stringify(zodToJsonSchema(zodSchema), null, 2));
+console.log("\nTypeBox.StringEnum:", JSON.stringify(typeboxHelper, null, 2));