feat(simulation): integrate knowledge graph into observer snapshot (#366)

VisibleEntity now carries relationship state (D-033 entity color) and
observation type (Visible vs Remembered). compute_observer_snapshot
queries the player's KnowledgeGraph to overlay relationship data on
visible entities and include remembered (not-in-LOS) entities as fog
ghosts at their last known position. Regenerated msgpack fixtures.

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

server/src/bridge/mod.rs

@@ -89,6 +89,8 @@ pub fn generate_snapshot(
             z,
             kind,
             visibility: VisibilitySector::Forward,
+            relationship: RelationshipState::Unknown,
+            observation: EntityVisibility::Visible,
         });
     }