docs: create milestone v1.1 TDD & Correctness (5 phases)

Phases:
- 8. DAG System TDD: Performance/edge case tests with 10k+ objects
- 9. Trip Planner Modes TDD: By dates, must-see games, start/end cities
- 10. Trip Builder Options TDD: Repeat cities, must-stops
- 11. Itinerary & Constraints TDD: Travel directions, driving limits
- 12. Integration Validation: End-to-end scenarios, regression suite

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

.planning/STATE.md

@@ -5,16 +5,16 @@
 See: .planning/PROJECT.md (updated 2026-01-10)
 
 **Core value:** Every game must correctly link to its teams and stadium — a game at the wrong venue or with broken team links ruins trip planning.
-**Current focus:** Planning next milestone
+**Current focus:** v1.1 TDD & Correctness — Phase 8
 
 ## Current Position
 
-Phase: N/A (between milestones)
-Plan: N/A
-Status: Ready to plan next milestone
-Last activity: 2026-01-10 — v1.0 Data Pipeline shipped
+Phase: 8 of 12 (DAG System TDD)
+Plan: Not started
+Status: Ready to plan
+Last activity: 2026-01-10 — Milestone v1.1 TDD & Correctness created
 
-Progress: v1.0 complete — 15 plans across 8 phases
+Progress: ░░░░░░░░░░ 0%
 
 ## Shipped Milestones
 
@@ -36,9 +36,13 @@ Decisions are logged in PROJECT.md Key Decisions table.
 
 None.
 
+### Roadmap Evolution
+
+- Milestone v1.1 TDD & Correctness created: Test-driven validation of trip planning engine, 5 phases (Phase 8-12)
+
 ## Session Continuity
 
 Last session: 2026-01-10
-Stopped at: v1.0 milestone shipped
-Resume file: N/A
-Next action: /gsd:discuss-milestone or /gsd:new-milestone to plan next work
+Stopped at: Milestone v1.1 initialization
+Resume file: None
+Next action: /gsd:plan-phase 8 to plan first phase