add sandboxes announcement to changelog

src/content/changelog/agents/2025-06-24-announcing-sandboxes.mdx

@@ -0,0 +1,39 @@
+---
+title: Run AI-generated code on-demand with Code Sandboxes (new)
+description: You can start creating sandboxes today by installing our new Sandbox package.
+products:
+  - agents
+  - workers
+  - workflows
+date: 2025-06-25T15:00:00Z
+---
+
+AI is supercharging app development for everyone, but we need a safe way to run untrusted, LLM-written code. We’re introducing [Sandboxes](https://www.npmjs.com/package/@cloudflare/sandbox), which let your Worker run actual processes in a secure, container-based environment.
+
+```ts
+import { getSandbox } from "@cloudflare/sandbox";
+export { Sandbox } from "@cloudflare/sandbox";
+
+export default {
+  async fetch(request: Request, env: Env) {
+    const sandbox = getSandbox(env.Sandbox, "my-sandbox");
+    return sandbox.exec("ls", ["-la"]);
+  },
+};
+```
+
+### Methods
+
+- `exec(command: string, args: string[], options?: { stream?: boolean })`:Execute a command in the sandbox.
+- `gitCheckout(repoUrl: string, options: { branch?: string; targetDir?: string; stream?: boolean })`: Checkout a git repository in the sandbox.
+- `mkdir(path: string, options: { recursive?: boolean; stream?: boolean })`: Create a directory in the sandbox.
+- `writeFile(path: string, content: string, options: { encoding?: string; stream?: boolean })`: Write content to a file in the sandbox.
+- `readFile(path: string, options: { encoding?: string; stream?: boolean })`: Read content from a file in the sandbox.
+- `deleteFile(path: string, options?: { stream?: boolean })`: Delete a file from the sandbox.
+- `renameFile(oldPath: string, newPath: string, options?: { stream?: boolean })`: Rename a file in the sandbox.
+- `moveFile(sourcePath: string, destinationPath: string, options?: { stream?: boolean })`: Move a file from one location to another in the sandbox.
+- `ping()`: Ping the sandbox.
+
+Sandboxes are still experimental. We're using them to explore how isolated, container-like workloads might scale on Cloudflare — and to help define the developer experience around them.
+
+You can try it today from your Worker, with just a few lines of code. Let us know what you build.