feat(perception): add cognitive delay system for fog recognition (#423)

New CognitiveDelay component buffers perception events before emitting
KnowledgeEvents. Normal delay: 6 ticks (0.6s), urgent: 3 ticks (0.3s).
Drain system runs after emit_observation_events, before process_knowledge_events.

Adds pending_recognitions to ObserverSnapshot (protocol v7) for client
fog entity visualization. Includes cancellation when entity leaves LOS.

Monologue fires during delay (not after) per D-060 — cross-system
wiring deferred to follow-up ticket #451.

Ref: D-060 (cognitive delay), D-031 (10 tps), D-059 (fog layers)

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

server/tests/gen_fixtures.rs

@@ -33,6 +33,7 @@ fn fixture_snapshot(tick: u64, entities: Vec<VisibleEntity>) -> ObserverSnapshot
         visible_tiles: vec![],
         nearby_interactions: vec![],
         current_monologue: None,
+        pending_recognitions: vec![],
     }
 }
 
@@ -200,6 +201,7 @@ fn generate_msgpack_fixtures() {
         ],
         nearby_interactions: vec![],
         current_monologue: None,
+        pending_recognitions: vec![],
     };
     write_fixture(
         "snapshot_v2_full",
@@ -214,7 +216,10 @@ fn generate_msgpack_fixtures() {
         },
         PlayerInput {
             tick: 0,
-            action: PlayerAction::Interact { target_entity_id: None, verb: None },
+            action: PlayerAction::Interact {
+                target_entity_id: None,
+                verb: None,
+            },
         },
     ];
     write_fixture(