feat(client): add EntityKind::Player fixture and update multi-entity fixture

Server team added EntityKind::Player variant. Added snapshot_player
fixture and updated snapshot_multi_entity to include all 4 entity kinds
(Player, Npc, Object, Terrain) for complete D-030 Layer 1 coverage.

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

server/tests/gen_fixtures.rs

@@ -60,26 +60,49 @@ fn generate_msgpack_fixtures() {
         &rmp_serde::to_vec_named(&input_perception).unwrap(),
     );
 
+    // Snapshot with Player entity (EntityKind::Player added by server team)
+    let snapshot_player = ObserverSnapshot {
+        tick: 1,
+        entities: vec![VisibleEntity {
+            entity_id: 100,
+            x: 16.5,
+            y: 16.5,
+            z: 0,
+            kind: EntityKind::Player,
+        }],
+    };
+    write_fixture(
+        "snapshot_player",
+        &rmp_serde::to_vec_named(&snapshot_player).unwrap(),
+    );
+
     // Snapshot with multiple entities and all EntityKind variants
     let snapshot_multi = ObserverSnapshot {
         tick: 999,
         entities: vec![
             VisibleEntity {
                 entity_id: 1,
+                x: 16.5,
+                y: 16.5,
+                z: 0,
+                kind: EntityKind::Player,
+            },
+            VisibleEntity {
+                entity_id: 2,
                 x: 5.0,
                 y: 10.0,
                 z: 0,
                 kind: EntityKind::Npc,
             },
             VisibleEntity {
-                entity_id: 2,
+                entity_id: 3,
                 x: 15.5,
                 y: 3.0,
                 z: 1,
                 kind: EntityKind::Object,
             },
             VisibleEntity {
-                entity_id: 3,
+                entity_id: 4,
                 x: 0.0,
                 y: 0.0,
                 z: -1,