Fix nixos-rebuild sudo path mismatch

Use explicit /run/current-system/sw/bin/nixos-rebuild path instead of
'nixos-rebuild' command to match sudo rules exactly. This resolves
'command not allowed' errors when the command resolves to nix store paths.

agent/src/agent.rs

@@ -302,7 +302,7 @@ impl Agent {
             tokio::process::Command::new("sudo")
                 .arg("-u")
                 .arg("cm")
-                .arg("nixos-rebuild")
+                .arg("/run/current-system/sw/bin/nixos-rebuild")
                 .arg("switch")
                 .current_dir(working_dir)
                 .output()