fix: add platform-specific sysproc for Windows and macOS

sysproc_darwin.go

@@ -0,0 +1,12 @@
+package main
+
+import (
+	"os/exec"
+	"syscall"
+)
+
+func setCommandSysProcAttr(cmd *exec.Cmd) {
+	cmd.SysProcAttr = &syscall.SysProcAttr{
+		Setpgid: true,
+	}
+}

sysproc_linux.go

@@ -1,5 +1,3 @@
-//go:build !windows
-
 package main
 
 import (
@@ -7,9 +5,6 @@ import (
 	"syscall"
 )
 
-// setCommandSysProcAttr sets platform-specific process attributes.
-// On Linux: sets a new process group so child processes don't receive
-// terminal signals meant for the parent, and enables proper cleanup.
 func setCommandSysProcAttr(cmd *exec.Cmd) {
 	cmd.SysProcAttr = &syscall.SysProcAttr{
 		Setpgid: true,

sysproc_windows.go

@@ -0,0 +1,7 @@
+package main
+
+import "os/exec"
+
+func setCommandSysProcAttr(cmd *exec.Cmd) {
+	// Windows does not use Setpgid
+}