fix(client): address PR #141 review — parse-order, tween guard, test fixes

- Fix autoload parse-order violations: sim_bridge.gd, input_mapper.gd,
  audio_manager.gd now use load() for class_name types instead of
  direct references (LocalBridge, ServerProcess, Constants)
- Collapse redundant tween validity guard in dialogue_box.gd to
  is_instance_valid(panel) only
- Add clarifying comments to fog test resize assertions (8-tile
  padding trigger, 32x32 fixture assumption)
- Fix test_examine_display_sprint18 case 2: GameState.has() →
  "field" in GameState (Node vs Dictionary API)
- Fix test_game_state_sprint20: rename before_each → before_test
  (GdUnit4 lifecycle hook)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

client/scripts/autoloads/sim_bridge.gd

@@ -27,8 +27,8 @@ var _last_snapshot: Variant = null  # Most recent decoded snapshot (consumed by
 var _outbound_buffer: Array[Dictionary] = []  # Raw inputs awaiting batch encode + transport
 
 # Transport layer (non-test mode)
-var _bridge: LocalBridge = null
-var _server: ServerProcess = null
+var _bridge = null  # LocalBridge
+var _server = null  # ServerProcess
 var _connect_retries: int = 0
 var _retry_timer: float = 0.0
 var _handshake_start_usec: int = 0
@@ -126,7 +126,8 @@ func connect_to_sim() -> void:
 
 	# Spawn server subprocess
 	if not server_path.is_empty():
-		_server = ServerProcess.new()
+		var SP := load("res://scripts/protocol/server_process.gd")
+		_server = SP.new()
 		# Server reads first positional arg as bind address (e.g. "127.0.0.1:9876").
 		# D-085 (#258): pass --game-id <id> so server logs use the same session identifier.
 		var args := ["127.0.0.1:" + str(server_port)]
@@ -159,7 +160,8 @@ func disconnect_from_sim() -> void:
 
 # Attempt TCP connection. Called from _process() during CONNECTING state.
 func _try_connect() -> void:
-	_bridge = LocalBridge.new()
+	var LB := load("res://scripts/protocol/local_bridge.gd")
+	_bridge = LB.new()
 	var err := _bridge.connect_to_server("127.0.0.1", server_port)
 	if err != OK:
 		push_warning(