fix(bridge): use named MessagePack format for wire compatibility

Client-side Protocol.gd expects rmp_serde::to_vec_named() (maps with
string keys), but LocalBridge was using to_vec() (compact positional
arrays). Fix send_snapshot and update all test serialization calls to
match actual wire format. Also change EOF from Ok(vec![]) to
BridgeError::Transport so bridge systems can detect disconnects.

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

server/src/bridge/local.rs

@@ -81,7 +81,7 @@ impl LocalBridge {
 
 impl SimBridge for LocalBridge {
     fn send_snapshot(&self, snapshot: &ObserverSnapshot) -> Result<(), BridgeError> {
-        let payload = rmp_serde::to_vec(snapshot)?;
+        let payload = rmp_serde::to_vec_named(snapshot)?;
 
         let mut writer = self.writer.lock().expect("writer mutex poisoned");
         write_framed(writer.get_mut(), &payload)?;
@@ -99,10 +99,7 @@ impl SimBridge for LocalBridge {
                 tracing::trace!("received {} inputs", inputs.len());
                 Ok(inputs)
             }
-            None => {
-                tracing::trace!("received EOF, returning empty input vec");
-                Ok(Vec::new())
-            }
+            None => Err(BridgeError::Transport("client disconnected (EOF)".into())),
         }
     }
 }

server/tests/bridge_ipc.rs

@@ -106,7 +106,7 @@ fn input_roundtrip_over_unix_socket() {
         },
     ];
 
-    let payload = rmp_serde::to_vec(&inputs).expect("failed to serialize");
+    let payload = rmp_serde::to_vec_named(&inputs).expect("failed to serialize");
     write_framed(&mut writer, &payload).expect("failed to write frame");
 
     // Drop writer to close connection and signal EOF to server

server/tests/serialization.rs

@@ -15,7 +15,7 @@ fn observer_snapshot_roundtrip() {
         }],
     };
 
-    let bytes = rmp_serde::to_vec(&snapshot).expect("serialize");
+    let bytes = rmp_serde::to_vec_named(&snapshot).expect("serialize");
     let decoded: ObserverSnapshot = rmp_serde::from_slice(&bytes).expect("deserialize");
 
     assert_eq!(decoded.tick, 42);
@@ -30,7 +30,7 @@ fn player_input_roundtrip() {
         action: PlayerAction::MoveNorth,
     };
 
-    let bytes = rmp_serde::to_vec(&input).expect("serialize");
+    let bytes = rmp_serde::to_vec_named(&input).expect("serialize");
     let decoded: PlayerInput = rmp_serde::from_slice(&bytes).expect("deserialize");
 
     assert_eq!(decoded.tick, 100);
@@ -43,7 +43,7 @@ fn empty_snapshot_roundtrip() {
         entities: vec![],
     };
 
-    let bytes = rmp_serde::to_vec(&snapshot).expect("serialize");
+    let bytes = rmp_serde::to_vec_named(&snapshot).expect("serialize");
     let decoded: ObserverSnapshot = rmp_serde::from_slice(&bytes).expect("deserialize");
 
     assert_eq!(decoded.tick, 0);
@@ -73,11 +73,11 @@ fn all_player_action_variants_roundtrip() {
             tick: 1,
             action: action.clone(),
         };
-        let bytes = rmp_serde::to_vec(&input).expect("serialize");
+        let bytes = rmp_serde::to_vec_named(&input).expect("serialize");
         let decoded: PlayerInput = rmp_serde::from_slice(&bytes).expect("deserialize");
         assert_eq!(decoded.tick, 1);
         // Verify the variant survived by re-serializing and comparing bytes
-        let re_bytes = rmp_serde::to_vec(&decoded).expect("re-serialize");
+        let re_bytes = rmp_serde::to_vec_named(&decoded).expect("re-serialize");
         assert_eq!(bytes, re_bytes, "round-trip mismatch for action variant");
     }
 }
@@ -85,7 +85,12 @@ fn all_player_action_variants_roundtrip() {
 /// All EntityKind variants must survive MessagePack round-trip (D-030 Layer 1)
 #[test]
 fn all_entity_kind_variants_roundtrip() {
-    let kinds = vec![EntityKind::Npc, EntityKind::Object, EntityKind::Terrain];
+    let kinds = vec![
+        EntityKind::Player,
+        EntityKind::Npc,
+        EntityKind::Object,
+        EntityKind::Terrain,
+    ];
 
     for (i, kind) in kinds.into_iter().enumerate() {
         let entity = VisibleEntity {
@@ -99,9 +104,9 @@ fn all_entity_kind_variants_roundtrip() {
             tick: 0,
             entities: vec![entity],
         };
-        let bytes = rmp_serde::to_vec(&snapshot).expect("serialize");
+        let bytes = rmp_serde::to_vec_named(&snapshot).expect("serialize");
         let decoded: ObserverSnapshot = rmp_serde::from_slice(&bytes).expect("deserialize");
-        let re_bytes = rmp_serde::to_vec(&decoded).expect("re-serialize");
+        let re_bytes = rmp_serde::to_vec_named(&decoded).expect("re-serialize");
         assert_eq!(
             bytes, re_bytes,
             "round-trip mismatch for EntityKind variant"