doc: update the config.toml documentation for the Rust CLI in codex-rs/README.md (#795)

https://github.com/openai/codex/pull/793 had important information on
the `notify` config option that seemed worth memorializing, so this PR
updates the documentation about all of the configurable options in
`~/.codex/config.toml`.

codex-rs/README.md

@@ -20,3 +20,146 @@ This folder is the root of a Cargo workspace. It contains quite a bit of experim
 - [`exec/`](./exec) "headless" CLI for use in automation.
 - [`tui/`](./tui) CLI that launches a fullscreen TUI built with [Ratatui](https://ratatui.rs/).
 - [`cli/`](./cli) CLI multitool that provides the aforementioned CLIs via subcommands.
+
+## Config
+
+The CLI can be configured via `~/.codex/config.toml`. It supports the following options:
+
+### model
+
+The model that Codex should use.
+
+```toml
+model = "o3"  # overrides the default of "o4-mini"
+```
+
+### approval_policy
+
+Determines when the user should be prompted to approve whether Codex can execute a command:
+
+```toml
+# This is analogous to --suggest in the TypeScript Codex CLI
+approval_policy = "unless-allow-listed"
+```
+
+```toml
+# If the command fails when run in the sandbox, Codex asks for permission to
+# retry the command outside the sandbox.
+approval_policy = "on-failure"
+```
+
+```toml
+# User is never prompted: if the command fails, Codex will automatically try
+# something out. Note the `exec` subcommand always uses this mode.
+approval_policy = "never"
+```
+
+### sandbox_permissions
+
+List of permissions to grant to the sandbox that Codex uses to execute untrusted commands:
+
+```toml
+# This is comparable to --full-auto in the TypeScript Codex CLI, though
+# specifying `disk-write-platform-global-temp-folder` adds /tmp as a writable
+# folder in addition to $TMPDIR.
+sandbox_permissions = [
+    "disk-full-read-access",
+    "disk-write-platform-user-temp-folder",
+    "disk-write-platform-global-temp-folder",
+    "disk-write-cwd",
+]
+```
+
+To add additional writable folders, use `disk-write-folder`, which takes a parameter (this can be specified multiple times):
+
+```toml
+sandbox_permissions = [
+    # ...
+    "disk-write-folder=/Users/mbolin/.pyenv/shims",
+]
+```
+
+### disable_response_storage
+
+Currently, customers whose accounts are set to use Zero Data Retention (ZDR) must set `disable_response_storage` to `true` so that Codex uses an alternative to the Responses API that works with ZDR:
+
+```toml
+disable_response_storage = true
+```
+
+### notify
+
+Specify a program that will be executed to get notified about events generated by Codex. Note that the program will receive the notification argument as a string of JSON, e.g.:
+
+```json
+{
+  "type": "agent-turn-complete",
+  "turn-id": "12345",
+  "input-messages": ["Rename `foo` to `bar` and update the callsites."],
+  "last-assistant-message": "Rename complete and verified `cargo build` succeeds."
+}
+```
+
+The `"type"` property will always be set. Currently, `"agent-turn-complete"` is the only notification type that is supported.
+
+As an example, here is a Python script that parses the JSON and decides whether to show a desktop push notification using [terminal-notifier](https://github.com/julienXX/terminal-notifier) on macOS:
+
+```python
+#!/usr/bin/env python3
+
+import json
+import subprocess
+import sys
+
+
+def main() -> int:
+    if len(sys.argv) != 2:
+        print("Usage: notify.py <NOTIFICATION_JSON>")
+        return 1
+
+    try:
+        notification = json.loads(sys.argv[1])
+    except json.JSONDecodeError:
+        return 1
+
+    match notification_type := notification.get("type"):
+        case "agent-turn-complete":
+            assistant_message = notification.get("last-assistant-message")
+            if assistant_message:
+                title = f"Codex: {assistant_message}"
+            else:
+                title = "Codex: Turn Complete!"
+            input_messages = notification.get("input_messages", [])
+            message = " ".join(input_messages)
+            title += message
+        case _:
+            print(f"not sending a push notification for: {notification_type}")
+            return 0
+
+    subprocess.check_output(
+        [
+            "terminal-notifier",
+            "-title",
+            title,
+            "-message",
+            message,
+            "-group",
+            "codex",
+            "-ignoreDnD",
+            "-activate",
+            "com.googlecode.iterm2",
+        ]
+    )
+
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
+```
+
+To have Codex use this script for notifications, you would configure it via `notify` in `~/.codex/config.toml` using the appropriate path to `notify.py` on your computer:
+
+```toml
+notify = ["python3", "/Users/mbolin/.codex/notify.py"]
+```