docs: create milestone v2.0 Frontend (6 phases)

Phases:
- 16. frontend-scaffold: Vite project setup, tRPC client, shadcn/ui
- 17. initiative-dashboard: List view with status badges, progress bars
- 18. initiative-detail: Phase/task hierarchy accordion, queue actions
- 19. agent-inbox: Multi-question forms, answer submission, notifications
- 20. real-time-subscriptions: WebSocket transport, subscription hooks
- 21. polish-integration: Navigation, error/loading states, responsive layout

.planning/STATE.md

@@ -5,16 +5,16 @@
 See: .planning/PROJECT.md (updated 2026-02-04)
 
 **Core value:** Coordinate multiple Claude Code agents without losing track or stepping on each other.
-**Current focus:** Planning next milestone
+**Current focus:** v2.0 Frontend — Build web UI from wireframes
 
 ## Current Position
 
-Phase: All milestones complete (v1.0-v1.3)
-Plan: None active
-Status: Ready for next milestone
-Last activity: 2026-02-04 — v1.3 milestone archived
+Phase: 16 of 21 (Frontend Scaffold)
+Plan: Not started
+Status: Ready to plan
+Last activity: 2026-02-04 - Milestone v2.0 Frontend created
 
-Progress: ██████████ 100% (61 plans across 15 phases)
+Progress: ░░░░░░░░░░ 0%
 
 ## Performance Metrics
 
@@ -191,6 +191,7 @@ None yet.
 - Milestone v1.1 created: Test infrastructure, 3 phases (Phase 7-9)
 - Milestone v1.2 created: Architect & Multi-Question, 4 phases (Phase 10-13)
 - Milestone v1.3 created: Parallel Execution & UI Design, 2 phases (Phase 14-15)
+- Milestone v2.0 created: Frontend, 6 phases (Phase 16-21)
 
 ### Blockers/Concerns
 
@@ -199,5 +200,5 @@ None.
 ## Session Continuity
 
 Last session: 2026-02-04
-Stopped at: v1.3 archived, ready for next milestone
+Stopped at: Milestone v2.0 Frontend initialization
 Resume file: None