chore: improve docstring for --full-auto (#1379)

Reference `-c sandbox.mode=workspace-write` in the docstring and users
can read the config docs for `sandbox` for more information.

codex-rs/tui/src/cli.rs

@@ -25,7 +25,7 @@ pub struct Cli {
     #[arg(long = "ask-for-approval", short = 'a')]
     pub approval_policy: Option<ApprovalModeCliArg>,
 
-    /// Convenience alias for low-friction sandboxed automatic execution (-a on-failure, network-disabled sandbox that can write to cwd and TMPDIR)
+    /// Convenience alias for low-friction sandboxed automatic execution (-a on-failure, -c sandbox.mode=workspace-write).
     #[arg(long = "full-auto", default_value_t = false)]
     pub full_auto: bool,