fix(simulation): address PR #46 review — zone tests, doc accuracy, TBD comment

Add 3 zone enrichment tests to observer pipeline (tile inside zone,
tile outside zone, absent ZoneMap resource). Fix misleading Decay
Observatory doc comment that claimed Direct start when test starts at
KnowsDetails. Add production population TBD note on ZoneMap.

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

server/src/perception/observer/tests.rs

@@ -2466,3 +2466,116 @@ fn blocked_entities_sorted_ascending() {
     assert!(snapshot.blocked_entities.contains(&npc_b_sid.0));
     assert!(snapshot.blocked_entities.contains(&npc_c_sid.0));
 }
+
+// -----------------------------------------------------------------------
+// Zone enrichment tests (#523, D-077)
+// -----------------------------------------------------------------------
+
+#[test]
+fn zone_map_enriches_visible_tiles_with_zone_id() {
+    // Tile inside a zone should get zone_id = Some(zone_id)
+    use crate::simulation::zone::ZoneMap;
+
+    let mut world = setup_world(32, 32);
+    let mut zone_map = ZoneMap::default();
+    // Zone 42 covers (14..18, 14..18) — includes the observer's tile at (16,16)
+    zone_map.set_rect(14, 14, 4, 4, 0, 42);
+    world.insert_resource(zone_map);
+
+    world.spawn((
+        PlayerCharacter,
+        TilePosition::new(16, 16, 0),
+        Facing::default(),
+        KnowledgeGraph::new(),
+        NearbyInteractionBuffer::default(),
+        MonologueBuffer::default(),
+    ));
+
+    run_observer_pipeline(&mut world);
+
+    let buffer = world.resource::<SnapshotBuffer>();
+    let snapshot = buffer.snapshot.as_ref().unwrap();
+
+    // Observer's tile (16, 16) is inside zone 42
+    let observer_tile = snapshot
+        .visible_tiles
+        .iter()
+        .find(|t| t.x == 16 && t.y == 16 && t.z == 0)
+        .expect("observer tile should be visible");
+    assert_eq!(
+        observer_tile.zone_id,
+        Some(42),
+        "tile inside zone should have zone_id"
+    );
+}
+
+#[test]
+fn zone_map_tiles_outside_zone_get_none() {
+    // Tile outside any zone should get zone_id = None
+    use crate::simulation::zone::ZoneMap;
+
+    let mut world = setup_world(32, 32);
+    let mut zone_map = ZoneMap::default();
+    // Zone only covers (0..2, 0..2) — far from observer at (16,16)
+    zone_map.set_rect(0, 0, 2, 2, 0, 7);
+    world.insert_resource(zone_map);
+
+    world.spawn((
+        PlayerCharacter,
+        TilePosition::new(16, 16, 0),
+        Facing::default(),
+        KnowledgeGraph::new(),
+        NearbyInteractionBuffer::default(),
+        MonologueBuffer::default(),
+    ));
+
+    run_observer_pipeline(&mut world);
+
+    let buffer = world.resource::<SnapshotBuffer>();
+    let snapshot = buffer.snapshot.as_ref().unwrap();
+
+    // Observer's tile (16, 16) is outside any zone
+    let observer_tile = snapshot
+        .visible_tiles
+        .iter()
+        .find(|t| t.x == 16 && t.y == 16 && t.z == 0)
+        .expect("observer tile should be visible");
+    assert_eq!(
+        observer_tile.zone_id, None,
+        "tile outside any zone should have zone_id = None"
+    );
+}
+
+#[test]
+fn no_zone_map_resource_tiles_have_no_zone_id() {
+    // When ZoneMap resource is absent, all tiles should have zone_id = None
+    let mut world = setup_world(32, 32);
+    // Do NOT insert ZoneMap resource
+
+    world.spawn((
+        PlayerCharacter,
+        TilePosition::new(16, 16, 0),
+        Facing::default(),
+        KnowledgeGraph::new(),
+        NearbyInteractionBuffer::default(),
+        MonologueBuffer::default(),
+    ));
+
+    run_observer_pipeline(&mut world);
+
+    let buffer = world.resource::<SnapshotBuffer>();
+    let snapshot = buffer.snapshot.as_ref().unwrap();
+
+    assert!(
+        !snapshot.visible_tiles.is_empty(),
+        "should have visible tiles"
+    );
+    // All tiles should have zone_id = None when no ZoneMap exists
+    for tile in &snapshot.visible_tiles {
+        assert_eq!(
+            tile.zone_id, None,
+            "tile ({},{}) should have zone_id = None without ZoneMap resource",
+            tile.x, tile.y
+        );
+    }
+}