Merge remote-tracking branch 'origin/main' into client

# Conflicts:
#	CHANGELOG.md
#	client/scripts/autoloads/sim_bridge.gd

client/scripts/protocol/protocol.gd

@@ -9,6 +9,10 @@ class_name Protocol
 ##   Unit enum variants (no data) → bare strings ("MoveNorth", "Npc")
 ##   Data enum variants → single-element maps ({"UsePerceptionMode": "thermal"})
 
+## Protocol version — must match server PROTOCOL_VERSION in bridge/types.rs.
+## Reject snapshots where version != this value.
+const PROTOCOL_VERSION: int = 4
+
 
 # -- Decode: bytes from server → GDScript types --------------------------------
 
@@ -27,6 +31,12 @@ static func decode_snapshot(bytes: PackedByteArray) -> Variant:
 		push_error("Protocol: snapshot missing required fields")
 		return null
 
+	# Version check: reject snapshots from incompatible server
+	var version: Variant = raw.get("version")
+	if version != PROTOCOL_VERSION:
+		push_error("Protocol: version mismatch (got %s, expected %s). Server and client are out of sync." % [version, PROTOCOL_VERSION])
+		return null
+
 	var entities: Array[Dictionary] = []
 	var raw_entities: Array = raw["entities"]
 	var dropped := 0
@@ -44,8 +54,7 @@ static func decode_snapshot(bytes: PackedByteArray) -> Variant:
 	# in any realistic scenario (would require ~29 billion years at 10 ticks/game-minute per D-031).
 	var tick: int = raw["tick"]
 
-	# v2 fields — optional for backward compatibility
-	var version: Variant = raw.get("version")
+	# version already checked above; game_time for HUD display
 	var game_time: Variant = raw.get("game_time")
 
 	# player_facing: FacingDirection is a unit enum → bare string in rmp_serde