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/gen_fixtures.rs

@@ -37,6 +37,7 @@ fn fixture_snapshot(tick: u64, entities: Vec<VisibleEntity>) -> ObserverSnapshot
         dialogue_response: None,
         blocked_entities: vec![],
         scan_events: vec![],
+        sound_events: vec![],
     }
 }
 
@@ -208,6 +209,7 @@ fn generate_msgpack_fixtures() {
         dialogue_response: None,
         blocked_entities: vec![],
         scan_events: vec![],
+        sound_events: vec![],
     };
     write_fixture(
         "snapshot_v2_full",