refactor(server): decompose observer pipeline and fix interaction boundary

Extract visibility geometry into a separate system behind a
PerceptionQuery trait, enabling D-017 perception mode swapping.
Two-stage pipeline: compute_visibility_geometry writes to
VisibilityGeometry resource, compute_observer_snapshot reads it.

Remove KnowledgeGraph from compute_nearby_interactions (simulation
phase boundary violation). Verb availability stays in simulation;
POI-based priority adjustment moves to observer via
apply_poi_verb_priority helper.

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

server/src/perception/mod.rs

@@ -8,6 +8,7 @@ use bevy_ecs::schedule::IntoScheduleConfigs;
 pub mod interpretation;
 pub mod observation;
 pub mod observer;
+pub mod query;
 pub mod shadowcast;
 pub mod vision_cone;
 
@@ -18,6 +19,8 @@ pub struct PerceptionPlugin;
 impl Plugin for PerceptionPlugin {
     fn build(&self, app: &mut App) {
         app.init_resource::<interpretation::ObservationEventQueue>()
+            .init_resource::<query::VisibilityGeometry>()
+            .init_resource::<query::ActivePerceptionMode>()
             .add_systems(
                 Update,
                 interpretation::generate_observation_events