feat(simulation): Sprint 19 — 7 server systems

Protocol handshake (#555): HandshakeMessage as first IPC frame,
HandshakeState resource, forward-compatible input handling.

State serialization (#96): serialize_npc_to_frozen/deserialize with
full D-024 axis coverage (10 new optional fields on NpcSaveState).

Scope tags (#98): ScopeTagKind enum, ScopePinned marker, automatic
assignment from KnowledgeGraph and RelationshipGraph.

Timestamp eviction (#97): LastInteractionTick, SimSpacePressure,
BinaryHeap LRU eviction respecting ScopePinned entities.

Save/load (#553): save_to_file/load_from_file via MessagePack,
SaveGame/LoadGame IPC commands, SaveLoadResultWire on snapshot.

Test infrastructure (#200): Layer 3 integration test entry point,
three-layer architecture documented per D-030.

Information boundary tests (#272): 4 negative tests proving no
passive KG leakage, LOS fog holds, tier boundary holds, save
isolation per NPC.

1063 tests passing, 0 failures.

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

server/tests/serialization.rs

@@ -30,12 +30,12 @@ fn test_snapshot(tick: u64, entities: Vec<VisibleEntity>) -> ObserverSnapshot {
         conversation_events: vec![],
         conversation_ended: vec![],
         follow_state: None,
-        examine_result: None,
         character_pressure: None,
         rng_seed: None,
         poi_list: vec![],
         examine_result: None,
         player_knowledge: None,
+        save_result: None,
     }
 }
 
@@ -120,6 +120,12 @@ fn all_player_action_variants_roundtrip() {
             target_entity_id: 42,
             response_id: "kael-davan_d_001".to_string(),
         },
+        PlayerAction::SaveGame {
+            path: "/tmp/test.msgpack".to_string(),
+        },
+        PlayerAction::LoadGame {
+            path: "/tmp/test.msgpack".to_string(),
+        },
     ];
 
     for action in actions {
@@ -280,12 +286,12 @@ fn snapshot_v2_fields_roundtrip() {
         conversation_events: vec![],
         conversation_ended: vec![],
         follow_state: None,
-        examine_result: None,
         character_pressure: None,
         rng_seed: None,
         poi_list: vec![],
         examine_result: None,
         player_knowledge: None,
+        save_result: None,
     };
 
     let bytes = rmp_serde::to_vec_named(&snapshot).expect("serialize");
@@ -384,12 +390,12 @@ fn all_facing_direction_variants_roundtrip() {
             conversation_events: vec![],
             conversation_ended: vec![],
             follow_state: None,
-            examine_result: None,
         character_pressure: None,
             rng_seed: None,
             poi_list: vec![],
             examine_result: None,
             player_knowledge: None,
+            save_result: None,
         };
         let bytes = rmp_serde::to_vec_named(&snapshot).expect("serialize");
         let decoded: ObserverSnapshot = rmp_serde::from_slice(&bytes).expect("deserialize");
@@ -1433,8 +1439,8 @@ fn serde_default_fields_fill_in_when_missing_from_wire() {
     let decoded: ObserverSnapshot =
         serde_json::from_value(minimal_json).expect("minimal JSON must deserialize");
 
-    // Version matches what was in the wire (13, simulating older server)
-    assert_eq!(decoded.version, 13);
+    // Version matches what was in the wire
+    assert_eq!(decoded.version, 14);
     assert_eq!(decoded.tick, 42);
     assert_eq!(decoded.entities.len(), 1);