A 42-year-old woman from Delhi presents with a 6-month history of symmetric polyarthritis affecting her wrists, knees, and small joints of the hands. She reports morning stiffness lasting 2 hours. On examination, she has warm, swollen joints with reduced range of motion. Laboratory investigations show: ESR 68 mm/hr, CRP 12 mg/dL, RF 185 IU/mL (positive), anti-CCP antibodies 95 U/mL (positive). X-ray of hands shows juxta-articular osteopenia and early marginal erosions. Which of the following pathological processes is MOST directly responsible for the joint destruction observed in this patient?