feat: add platform-specific process attributes support (#411)

Fixes issues on Windows showing new windows for every process llama-swap spawns.

proxy/process_unix.go

@@ -0,0 +1,12 @@
+//go:build !windows
+
+package proxy
+
+import (
+	"os/exec"
+)
+
+// setProcAttributes sets platform-specific process attributes
+func setProcAttributes(cmd *exec.Cmd) {
+	// No-op on Unix systems
+}