Context

The Org Chart page (#778) supports CRUD via right-click context menus, but drag-drop reassignment of agents between departments is not yet implemented. The docs/design/page-structure.md defers inline graph editing to v0.6+, but the original issue (#778, absorbing #674) listed drag-drop as a deliverable.

Scope

• Drag agent nodes between department group nodes to reassign
• Visual feedback during drag: ghost preview, drop zone highlight (accent border + accent/5% background)
• Spring animation on drop settle (springBouncy preset)
• Invalid drop (outside any department) springs back to original position
• Optimistic update with rollback on API failure
• ARIA announcements for drag start/over/drop events

Design reference

• docs/design/ux-guidelines.md Section 3.4 (Drag-and-Drop spec)
• Issue feat: Org Chart page (living nodes, status, CRUD, department health) #778 "CRUD Operations" section

Dependencies

• Backend API endpoint for agent department reassignment (may be part of feat: Company page (department/agent management, consistent cards) #786)

Deliverables

• React Flow onNodeDrag + onNodeDragStop with department drop target detection
• Visual feedback (ghost, drop zone highlight, settle animation)
• Optimistic update with rollback
• Accessibility: ARIA live announcements
• Unit tests for drop target detection logic