docs(18): verification passed + mark phase complete

Phase-goal verification: 7/7 decision-contract truths confirmed (D-01..D-07).
Browser round-trip re-confirmed via Playwright e2e against the live stack.
Mark phase 18 complete in STATE.md and ROADMAP.md.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.planning/STATE.md

@@ -2,16 +2,16 @@
 gsd_state_version: 1.0
 milestone: v1.1
 milestone_name: Operability & Polish
-status: verifying
+status: completed
 stopped_at: Phase 18 Plan 03 complete — broker rewire done; plan 4 of 4 is next
-last_updated: "2026-06-15T02:46:09.819Z"
-last_activity: 2026-06-15
+last_updated: "2026-06-15T03:08:19.109Z"
+last_activity: 2026-06-15 -- Phase 18 marked complete
 progress:
   total_phases: 23
-  completed_phases: 10
-  total_plans: 36
+  completed_phases: 9
+  total_plans: 37
   completed_plans: 36
-  percent: 43
+  percent: 39
 ---
 
 # Project State
@@ -25,10 +25,10 @@ See: .planning/PROJECT.md (updated 2026-06-10)
 
 ## Current Position
 
-Phase: 18 (auto-timezone-detection-and-ability-to-change-timezone) — EXECUTING
+Phase: 18 — COMPLETE
 Plan: 4 of 4
-Status: Phase complete — ready for verification
-Last activity: 2026-06-15
+Status: Phase 18 complete
+Last activity: 2026-06-15 -- Phase 18 marked complete
 
 ### ✅ Resolved Checkpoint — Phase 15 Plan 15-03 Task 2 (human-action)