- TriplePane component with two resizable dividers, localStorage persistence, mobile tabs
- SprintBoardClient replaces SprintBacklogClient + PlanningRightClient
- Left panel: Product Backlog (PBIs with stories to add to sprint)
- Middle panel: Sprint Backlog (stories in sprint, click to select, sortable)
- Right panel: TaskList for selected story
- /sprint/planning redirects to /sprint
- Remove PlanningLeft, PlanningRightClient, SprintBacklogClient
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
