feat: use sudo and --restart for macOS softwareupdate (topgrade-rs#627)

Run `softwareupdate` through sudo and add the `--restart` flag so
that the system can reboot automatically when a macOS update requires
it. This aligns with the behavior described in the softwareupdate(8)
man page.

Based-on-PR: topgrade-rs#627
Original-author: Steve Lau <stevelauc@outlook.com>

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: barkleesanders

src/steps/os/macos.rs

@@ -52,8 +52,9 @@ pub fn upgrade_macos(ctx: &ExecutionContext) -> Result<()> {
         }
     }
 
-    let mut command = ctx.execute("softwareupdate");
-    command.args(["--install", "--all"]);
+    let sudo = ctx.require_sudo()?;
+    let mut command = sudo.execute(ctx, "softwareupdate")?;
+    command.args(["--install", "--all", "--restart"]);
 
     if should_ask {
         command.arg("--no-scan");