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/input_mapper.gd

@@ -184,10 +184,11 @@ func _update_facing_from_mouse() -> void:
 	if vp == null:
 		return
 	var canvas_xf := vp.get_canvas_transform()
-	var player_world_px := GameState.player_position * Constants.TILE_SIZE
-	var player_screen := canvas_xf * player_world_px
-	var mouse_screen := vp.get_mouse_position()
-	var delta := mouse_screen - player_screen
+	var C := load("res://scripts/constants.gd")
+	var player_world_px: Vector2 = GameState.player_position * C.TILE_SIZE
+	var player_screen: Vector2 = canvas_xf * player_world_px
+	var mouse_screen: Vector2 = vp.get_mouse_position()
+	var delta: Vector2 = mouse_screen - player_screen
 	# Only update if mouse is meaningfully distant from player (avoid jitter at center)
 	if delta.length_squared() > 4.0:
 		facing_angle = delta.angle()