refactor: implement cross-platform abstraction for process management, media control, and startup configuration (TESTING)

internal/windows/process.go

@@ -0,0 +1,16 @@
+//go:build windows
+package windows
+
+import "syscall"
+
+// IsProcessRunning checks if a process with the given PID exists on Windows.
+func IsProcessRunning(pid int) bool {
+	const PROCESS_QUERY_LIMITED_INFORMATION = 0x1000
+
+	handle, err := syscall.OpenProcess(PROCESS_QUERY_LIMITED_INFORMATION, false, uint32(pid))
+	if err != nil {
+		return false
+	}
+	syscall.CloseHandle(handle)
+	return true
+}