docs: update codex-rs/README.md to list new features in the Rust CLI (openai#1267)

Let users know about what the Rust CLI supports that the TypeScript CLI
doesn't!

Author: bolinfest

codex-rs/README.md

@@ -13,20 +13,52 @@ codex
 
 You can also download a platform-specific release directly from our [GitHub Releases](https://github.com/openai/codex/releases).
 
-## Config
+## What's new in the Rust CLI
 
-Codex supports a rich set of configuration options. See [`config.md`](./config.md) for details.
+While we are [working to close the gap between the TypeScript and Rust implementations of Codex CLI](https://github.com/openai/codex/issues/1262), note that the Rust CLI has a number of features that the TypeScript CLI does not!
 
-## Model Context Protocol Support
+### Config
+
+Codex supports a rich set of configuration options. Note that the Rust CLI uses `config.toml` instead of `config.json`. See [`config.md`](./config.md) for details.
+
+### Model Context Protocol Support
 
 Codex CLI functions as an MCP client that can connect to MCP servers on startup. See the [`mcp_servers`](./config.md#mcp_servers) section in the configuration documentation for details.
 
-It is still experimental, but you can also launch Codex as an MCP _server_ by running `codex mcp`. Using the [`@modelcontextprotocol/inspector`](https://github.com/modelcontextprotocol/inspector) is
+It is still experimental, but you can also launch Codex as an MCP _server_ by running `codex mcp`. Use the [`@modelcontextprotocol/inspector`](https://github.com/modelcontextprotocol/inspector) to try it out:
 
 ```shell
 npx @modelcontextprotocol/inspector codex mcp
 ```
 
+### Notifications
+
+You can enable notifications by configuring a script that is run whenever the agent finishes a turn. The [notify documentation](./config.md#notify) includes a detailed example that explains how to get desktop notifications via [terminal-notifier](https://github.com/julienXX/terminal-notifier) on macOS.
+
+### `codex exec` to run Codex programmatially/non-interactively
+
+To run Codex non-interactively, run `codex exec PROMPT` (you can also pass the prompt via `stdin`) and Codex will work on your task until it decides that it is done and exits. Output is printed to the terminal directly. You can set the `RUST_LOG` environment variable to see more about what's going on.
+
+### `--cd`/`-C` flag
+
+Sometimes it is not convenient to `cd` to the directory you want Codex to use as the "working root" before running Codex. Fortunately, `codex` supports a `--cd` option so you can specify whatever folder you want. You can confirm that Codex is honoring `--cd` by double-checking the **workdir** it reports in the TUI at the start of a new session.
+
+### Experimenting with the Codex Sandbox
+
+To test to see what happens when a command is run under the sandbox provided by Codex, we provide the following subcommands in Codex CLI:
+
+```
+# macOS
+codex debug seatbelt [-s SANDBOX_PERMISSION]... [COMMAND]...
+
+# Linux
+codex debug landlock [-s SANDBOX_PERMISSION]... [COMMAND]...
+```
+
+You can experiment with different values of `-s` to see what permissions the `COMMAND` needs to execute successfully.
+
+Note that the exact API for the `-s` flag is currently in flux. See https://github.com/openai/codex/issues/1248 for details.
+
 ## Code Organization
 
 This folder is the root of a Cargo workspace. It contains quite a bit of experimental code, but here are the key crates: