fix(simulation): address PR #10 review — plugin wiring, stale reset, warnings

- Register KnowledgePlugin in main.rs and game_loop test (Tyre critical)
- Add KnowledgeGraph component to player spawn (Tyre critical)
- Reset Stale -> Active on fresh direct observation (Hoshe warning)
- Make registry/queue non-optional in emit_observation_events (Tyre/Hoshe)
- Add tracing::warn for missing EntityRegistry entries (Hoshe warning)
- Replace HashSet with Vec for small entity ID lookups (Hoshe suggestion)
- Add const static assertion for KnowledgeConfidence ordering (Hoshe)
- Add is_empty() and known_facts_iter() to KnowledgeGraph (Tyre)
- Add decay_skips_non_minute_ticks and observe_resets_stale tests (Hoshe)

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

server/src/main.rs

@@ -6,6 +6,7 @@ use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
 
 use settled_reach_server::bridge::tcp::TcpBridge;
 use settled_reach_server::bridge::{BridgePlugin, BridgeResource, ServerRunning};
+use settled_reach_server::knowledge::{KnowledgeGraph, KnowledgePlugin};
 use settled_reach_server::perception::vision_cone::Facing;
 use settled_reach_server::simulation::movement::{PlayerCharacter, TilePosition, WalkabilityMap};
 use settled_reach_server::simulation::SimulationPlugin;
@@ -38,10 +39,15 @@ fn main() {
     let mut app = App::new();
     app.add_plugins(SimulationPlugin);
     app.add_plugins(BridgePlugin);
+    app.add_plugins(KnowledgePlugin);
     app.insert_resource(BridgeResource::new(bridge));
     app.insert_resource(WalkabilityMap::new(32, 32, 1));
-    app.world_mut()
-        .spawn((PlayerCharacter, TilePosition::new(16, 16, 0), Facing::default()));
+    app.world_mut().spawn((
+        PlayerCharacter,
+        TilePosition::new(16, 16, 0),
+        Facing::default(),
+        KnowledgeGraph::new(),
+    ));
 
     tracing::info!("Simulation initialized, entering game loop");