Tasks completed: 2/2 - Create SortOrderProvider utility - Add day derivation methods to Trip SUMMARY: .planning/phases/01-semantic-position-model/01-01-SUMMARY.md
Phases: 1. Semantic Position Model: DATA-*, PERS-* (foundation) 2. Constraint Validation: CONS-* (rules engine) 3. Visual Flattening: FLAT-* (display bridge) 4. Drag Interaction: DRAG-* (UI layer) All 23 v1 requirements mapped to phases.