fix(simulation): address PR #39 review — 3 warnings + 6 suggestions

Warnings fixed:
- contraband.rs: scan event now always emits even when NPC already
  knows (was skipped by early `continue`). Contract matches doc.
- test_world/mod.rs: ScanEventBuffer added to player spawn bundle
  so check_contraband_scan doesn't silently no-op in gauntlet mode.
- npc/mod.rs → simulation/mod.rs: moved check_contraband_scan
  registration to SimulationPlugin (operates on player inventory and
  snapshot pipeline, consistent with process_talk_interaction).

Suggestions addressed:
- cross_room_transitions.rs T1: clarified standalone position vs
  constants.rs observer position in comment.
- dialogue.rs: Vec<&str> dedup replaced with BTreeSet<&str> for
  deterministic iteration (project convention).
- contraband.rs: added test for multiple simultaneous ScanAuthority
  NPCs in range (564 tests total).
- dialogue.rs: doc-comment on relationship_to_trust explaining
  KnowledgeConfidence ordering and Suspects default.
- cross_room_transitions.rs T5: noted direct KG API usage vs full
  perception system.
- sprint_gauntlet.rs: documented intentional Contentment { level: 0 }.
- content_scaling.rs: noted GAUNTLET_NPC_COUNT is manually maintained.
- contraband.rs: doc-comment on cross-plugin registration rationale.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/test_world/mod.rs

@@ -58,6 +58,7 @@ use crate::simulation::inventory::ItemName;
 #[cfg(feature = "gauntlet")]
 use crate::simulation::listening::ListeningFocus;
 #[cfg(feature = "gauntlet")]
+use crate::simulation::contraband::ScanEventBuffer;
 use crate::simulation::monologue::{MonologueBuffer, MonologueState, SprintAnomalyQueue};
 #[cfg(feature = "gauntlet")]
 use crate::simulation::movement::{PlayerCharacter, TilePosition, WalkabilityMap};
@@ -148,6 +149,7 @@ pub fn setup_gauntlet(app: &mut App) {
             MonologueState::default(),
             MonologueBuffer::default(),
             SprintAnomalyQueue::default(),
+            ScanEventBuffer::default(),
             CognitiveDelay::default(),
             ListeningFocus::new(player_pos),
             profile,

server/src/test_world/rooms/sprint_gauntlet.rs

@@ -58,7 +58,7 @@ pub fn spawn_entities(app: &mut App, registry: &mut EntityRegistry) {
                 intensity: 4,
                 description: "Sprint Gauntlet: visible NPC during sprint".to_string(),
             },
-            Contentment { level: 0 },
+            Contentment { level: 0 }, // Neutral — test NPC, contentment not load-bearing here
             ToleranceThreshold {
                 current_stress: 10,
                 threshold: 50,