feat(simulation): #523 add zone_id to ObserverSnapshot (D-077, protocol v11)

Server-tracked zone_id on VisibleTile for D-073 zone crossfade and
D-059 deep fog temperature tint. ZoneMap resource backed by BTreeMap,
observer enrichment in snapshot assembly. Backwards-compatible: v10
payloads deserialize with zone_id: None.

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

server/src/perception/observer/mod.rs

@@ -26,6 +26,7 @@ use crate::simulation::rng::SimRng;
 use crate::simulation::sound::SoundEventQueue;
 use crate::simulation::stance::Stance;
 use crate::simulation::time::SimulationTime;
+use crate::simulation::zone::ZoneMap;
 
 /// Compute visibility geometry using the active perception mode.
 /// Stage 1 of the observer pipeline: FOV + vision cone → VisibilityGeometry.
@@ -61,6 +62,7 @@ pub fn compute_observer_snapshot(
     time: Res<SimulationTime>,
     geometry: Res<VisibilityGeometry>,
     registry: Res<EntityRegistry>,
+    zone_map: Option<Res<ZoneMap>>,
     sound_queue: Option<Res<SoundEventQueue>>,
     mut observer_query: Query<
         (
@@ -221,6 +223,19 @@ pub fn compute_observer_snapshot(
     // Sort entities by entity_id for deterministic snapshot ordering (#457)
     entities.sort_by_key(|e| e.entity_id);
 
+    // Enrich tiles with zone_id from ZoneMap (D-077, D-073)
+    let visible_tiles = match zone_map.as_deref() {
+        Some(zm) => geometry
+            .visible_tiles
+            .iter()
+            .map(|t| VisibleTile {
+                zone_id: zm.zone_at(t.x, t.y, t.z),
+                ..t.clone()
+            })
+            .collect(),
+        None => geometry.visible_tiles.clone(),
+    };
+
     buffer.snapshot = Some(ObserverSnapshot {
         version: crate::bridge::types::PROTOCOL_VERSION,
         tick: time.tick,
@@ -229,7 +244,7 @@ pub fn compute_observer_snapshot(
         player_stance: stance_opt.map(|s| s.0).unwrap_or_default(),
         player_inventory,
         entities,
-        visible_tiles: geometry.visible_tiles.clone(),
+        visible_tiles,
         nearby_interactions,
         current_monologue,
         pending_recognitions,

server/src/perception/query.rs

@@ -83,6 +83,7 @@ impl PerceptionQuery for NaturalVision {
                     z,
                     visibility: sector,
                     tile_kind,
+                    zone_id: None,
                 }
             })
             .collect();