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/audio_manager.gd

@@ -231,7 +231,8 @@ func play_sound_event(event_type: String, world_tile_pos: Vector2) -> void:
 	var asset_key: String = SOUND_EVENT_ASSETS.get(event_type, "")
 	if asset_key.is_empty():
 		return
-	play_at(asset_key, world_tile_pos * Constants.TILE_SIZE)
+	var C := load("res://scripts/constants.gd")
+	play_at(asset_key, world_tile_pos * C.TILE_SIZE)
 
 
 # --- Playback: spatial (D-018 close-range) ---