feat(simulation): sprint 12 server — tier system, sound events, KG access, line previewer

Implements 4 completed tickets + partial progress on 2 more:

- #93 Tier marker components (ActiveSim, BackgroundSim, StateSaved + TierPlugin)
- #138 Information tag schema (ObserverAccess enum in knowledge/types.rs)
- #124 Sound event system (SoundEventEmitter, SoundEventQueue, bridge wiring)
- #193 Line previewer CLI (line_preview binary with filter/explain/sequence modes)
- #94 Active tier simulation (in progress — With<ActiveSim> filters)
- #139 Component-level access control (in progress — filter_by_access)

Updates snapshot fixtures and test golden files for new sound_events field.

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

server/src/perception/observer/mod.rs

@@ -21,6 +21,7 @@ use crate::simulation::interaction::NearbyInteractionBuffer;
 use crate::simulation::inventory::{CarriedBy, InventorySlot, ItemName};
 use crate::simulation::monologue::{MonologueBuffer, SprintAnomalyQueue};
 use crate::simulation::movement::{PlayerCharacter, TilePosition, WalkabilityMap};
+use crate::simulation::sound::SoundEventQueue;
 use crate::simulation::stance::Stance;
 use crate::simulation::time::SimulationTime;
 
@@ -56,6 +57,7 @@ pub fn compute_observer_snapshot(
     time: Res<SimulationTime>,
     geometry: Res<VisibilityGeometry>,
     registry: Res<EntityRegistry>,
+    sound_queue: Option<Res<SoundEventQueue>>,
     mut observer_query: Query<
         (
             Entity,
@@ -176,6 +178,14 @@ pub fn compute_observer_snapshot(
         .map(|buf| buf.take())
         .unwrap_or_default();
 
+    // Collect sound events audible to the observer (D-038, #124).
+    // Filter by D-018 range: only events the player can hear based on distance.
+    let sound_events = if let Some(ref queue) = sound_queue {
+        queue.audible_at(_observer_pos).cloned().collect()
+    } else {
+        Vec::new()
+    };
+
     // Build pending recognitions from CognitiveDelay (#423, D-060)
     let pending_recognitions = cognitive_delay_opt
         .map(|delay| {
@@ -215,6 +225,7 @@ pub fn compute_observer_snapshot(
         dialogue_response,
         blocked_entities,
         scan_events,
+        sound_events,
     });
 }