docs: mark simulation architecture gate complete

- Update ACTION_SYSTEM_ARCHITECTURE.md to describe the active-position
  contract and visual lifecycle proof
- Mark BUILD_IN_PUBLIC_PLAN.md systems-gate section complete
- Mark LEARNING_ROADMAP.md architecture-gate section complete and
  renumber post-gate implementation sequence
- Update PROJECT_CONTEXT.md immediate-milestone section to reflect
  completed gate and next food-loop milestone
- Update SIMULATION_STATE_SCHEMA.md with NPCStateRecord v2 details
- Update ADR 0001 checklist to mark active-position sync done

docs/BUILD_IN_PUBLIC_PLAN.md

@@ -352,7 +352,7 @@ river, and waterfall silhouettes plus a temporary baked navigation loop. The
 Terrain3D seed remains flat; sculpt refinement and the final bake resume only
 after the architecture gate.
 
-### Systems gate — Harden simulation authority 🔶 in progress
+### Systems gate — Harden simulation authority ✅ complete
 
 After the scaffold, greybox, and navigation spike prove the world shape, pause
 visual production and complete the mandatory architecture gate from the
@@ -364,7 +364,7 @@ learning roadmap:
 - resource amount and reservation authority outside scene nodes; ✅
 - stable action/profession IDs and initial definitions; ✅
 - separate action selection, execution, target resolution, and visual travel; ✅
-- explicit active-position synchronization.
+- explicit active-position synchronization. ✅
 
 Do not solve this by moving simulation ownership into `JajceWorld`. The
 environment remains a presentation and active-world query surface.
@@ -375,6 +375,10 @@ The same scenario produces the same result without `main.tscn`; unloading a
 visual does not change authoritative state; current resource and movement
 behavior still pass regression tests.
 
+Completed with deterministic continuation, simulation-owned resources,
+definition-backed IDs, separated action responsibilities, active position
+synchronization, and visual unload/reload invariance tests.
+
 ### Phase 3 — Establish the beauty baseline
 
 Add only the highest-value presentation: