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/content/spawn.rs

@@ -30,6 +30,7 @@ use crate::knowledge::types::{
 use crate::npc;
 use crate::simulation::interaction::Interactable;
 use crate::simulation::movement::TilePosition;
+use crate::simulation::tier::ActiveSim;
 use crate::simulation::time::DayPhase;
 
 /// Stable content identifier from YAML (e.g., "kael-davan", "sera-venn").
@@ -103,6 +104,10 @@ fn spawn_npc(world: &mut World, profile: &types::NpcProfile, result: &mut SpawnR
     // Default position — will be overridden by routine system on first phase transition
     entity_commands.insert(TilePosition::new(0, 0, 0));
 
+    // All spawned NPCs start in the Active tier (D-026, #94).
+    // The tier transition system (#99) will demote NPCs that are far from the player.
+    entity_commands.insert(ActiveSim);
+
     // Mark NPC as interactable for proximity-based verb detection (#413)
     entity_commands.insert(Interactable);