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/tests/serialization.rs

@@ -26,6 +26,7 @@ fn test_snapshot(tick: u64, entities: Vec<VisibleEntity>) -> ObserverSnapshot {
         dialogue_response: None,
         blocked_entities: vec![],
         scan_events: vec![],
+        sound_events: vec![],
     }
 }
 
@@ -254,6 +255,7 @@ fn snapshot_v2_fields_roundtrip() {
         dialogue_response: None,
         blocked_entities: vec![],
         scan_events: vec![],
+        sound_events: vec![],
     };
 
     let bytes = rmp_serde::to_vec_named(&snapshot).expect("serialize");
@@ -308,7 +310,7 @@ fn protocol_version_constant_matches_snapshot() {
     let snapshot = test_snapshot(0, vec![]);
     assert_eq!(snapshot.version, PROTOCOL_VERSION);
     assert_eq!(
-        PROTOCOL_VERSION, 9,
+        PROTOCOL_VERSION, 10,
         "bump this assertion when protocol version changes"
     );
 }
@@ -348,6 +350,7 @@ fn all_facing_direction_variants_roundtrip() {
             dialogue_response: None,
             blocked_entities: vec![],
             scan_events: vec![],
+            sound_events: vec![],
         };
         let bytes = rmp_serde::to_vec_named(&snapshot).expect("serialize");
         let decoded: ObserverSnapshot = rmp_serde::from_slice(&bytes).expect("deserialize");