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/ACTION_SYSTEM_ARCHITECTURE.md

@@ -63,16 +63,22 @@ targets, and translates presentation callbacks into simulation transitions.
 Further decomposition should follow measured pressure rather than splitting it
 into managers for their own sake.
 
-## Remaining architecture-gate gap
+## Active-position contract
 
-The resolver currently asks WorldViewManager for a visual's position at target
-request time. SimNPC also stores a position, but active movement is not yet
-synchronized back through an explicit authority contract.
+NpcVisual emits active position changes after successful movement.
+WorldViewManager forwards those facts through
+`SimulationManager.synchronize_npc_position()`. Arrival, navigation failure,
+and visual unload also perform a final synchronization.
 
-The next phase must:
+SimNPC stores both authoritative position and the resolved travel destination.
+The destination is versioned simulation state, so reloading a visual resumes
+the same route request without rerolling wander, resolving another resource, or
+changing a reservation.
 
-- define when active position is written to simulation state;
-- preserve the last authoritative position when a visual unloads;
-- spawn a reloaded visual from that position;
-- prove visual unload/reload does not change action, target, reservation, or
-  position state.
+`tests/npc_visual_lifecycle_test.gd` proves that visual unload/reload preserves
+action, target ID, travel destination, resource reservation, position, and
+state checksum.
+
+Unloaded NPCs do not yet resolve abstract travel time; they remain in their
+current task state until an active visual or a future simulation-LOD travel
+system advances them.