A 28‑year‑old man presents with sudden onset sharp right‑sided pleuritic chest pain and dyspnoea that began at rest. He is tall and thin, a non‑smoker with no past history. Examination shows reduced breath sounds and hyperresonance over the right hemithorax; he is haemodynamically stable with oxygen saturation 97% on room air. Chest X‑ray reveals a right primary spontaneous pneumothorax with a visible rim of 1.5 cm from lung edge to chest wall at the hilum. According to standard management guidance, what is the most appropriate initial management?