A 62-year-old woman from Delhi presents with a 4-month history of progressive dysphagia and retrosternal chest pain. Upper endoscopy reveals a 6 cm infiltrative lesion at the gastroesophageal junction with involvement of the lower esophagus. Biopsy confirms adenocarcinoma of Siewert type II (true GE junction tumor). CT chest and abdomen shows T4bN3M0 disease (invasion of diaphragm and adjacent structures, extensive regional lymphadenopathy). After neoadjuvant chemotherapy (FLOT regimen), restaging CT shows partial response with borderline resectability. What is the most appropriate next step in management?