fix(simulation): address PR #42 review — 8 items from Hoshe and Tyre

1. Sound producers: document empty v0.1 pipeline explicitly (critical)
2. Routine tests: add ActiveSim to 3 tests that passed trivially
3. Rename _observer_pos → observer_pos (used at line 191)
4. Add FactionOnly positive test case (matching faction_id)
5. Fix stale doc comment "Current: 9" → 10 in ObserverSnapshot
6. Remove orphaned SimulationTier/LastInteraction/ScopeTag types
7. Add tracing::warn on FactionOnly non-numeric parse failure
8. Document Medium-range occlusion gap as TODO in audible_at
9. Insert SoundEventQueue in observer test setup_world

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

server/src/perception/observer/tests.rs

@@ -15,6 +15,7 @@ fn setup_world(width: i32, height: i32) -> World {
     world.init_resource::<EntityRegistry>();
     world.init_resource::<VisibilityGeometry>();
     world.init_resource::<ActivePerceptionMode>();
+    world.init_resource::<crate::simulation::sound::SoundEventQueue>();
     world
 }