docs(04): create phase 4 drag interaction plans

Phase 04: Drag Interaction
- 2 plans in 2 waves
- Plan 01: Migrate to modern drag-drop delegates, lift animation, haptics
- Plan 02: Themed insertion line, invalid zone feedback, snap-back animation

Ready for execution

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.planning/ROADMAP.md

@@ -71,8 +71,8 @@ Plans:
 **Plans:** 2 plans
 
 Plans:
-- [ ] 03-01-PLAN.md - Create ItineraryFlattener utility and refactor reloadData()
-- [ ] 03-02-PLAN.md - Add determinism tests for flattening behavior
+- [x] 03-01-PLAN.md - Create ItineraryFlattener utility and refactor reloadData()
+- [x] 03-02-PLAN.md - Add determinism tests for flattening behavior
 
 **Requirements:**
 - FLAT-01: Visual flattening sorts by sortOrder within each day
@@ -92,6 +92,12 @@ Plans:
 
 **Dependencies:** Phase 3 (flattening provides row-to-semantic translation)
 
+**Plans:** 2 plans
+
+Plans:
+- [ ] 04-01-PLAN.md - Migrate to modern drag-drop delegates with lift animation and haptics
+- [ ] 04-02-PLAN.md - Add themed insertion line, invalid zone feedback, and snap-back animation
+
 **Requirements:**
 - DRAG-01: Lift animation on grab (shadow + slight scale)
 - DRAG-02: Insertion line appears between items showing drop target
@@ -117,10 +123,10 @@ Plans:
 |-------|--------|--------------|-----------|
 | 1 - Semantic Position Model | Complete | 8 | 8 |
 | 2 - Constraint Validation | Complete | 4 | 4 |
-| 3 - Visual Flattening | In Progress | 3 | 0 |
-| 4 - Drag Interaction | Not Started | 8 | 0 |
+| 3 - Visual Flattening | Complete | 3 | 3 |
+| 4 - Drag Interaction | Planned | 8 | 0 |
 
-**Total:** 12/23 requirements completed
+**Total:** 15/23 requirements completed
 
 ---
 *Roadmap created: 2026-01-18*