Give every script a class name and use it for typed references

The popups, the volume slider, the player name field and the main window get
a class_name, so the main window and the quiz hold them by their real type
instead of Control. The classes already use the names the files will get.

AboutWindow.gd

@@ -1,3 +1,4 @@
+class_name AboutPopup
 extends PopupWindow
 
 @onready

MainWindow.gd

@@ -1,3 +1,4 @@
+class_name MainWindow
 extends Control
 ## The main window: the top bar, the popups opened from it and the quiz below it.
 ##
@@ -11,22 +12,22 @@ var top_bar: TopBar = $TopBar
 var quiz: Quiz = $Quiz
 
 @onready
-var search_view: Control = $Search
+var search_view: SearchPopup = $Search
 
 @onready
-var sync_window: Control = %SyncWindow
+var sync_window: SyncPopup = %SyncWindow
 
 @onready
-var shortcuts_window: Control = %ShortcutsWindow
+var shortcuts_window: ShortcutsPopup = %ShortcutsWindow
 
 @onready
-var qr_window: Control = %QRWindow
+var qr_window: QRPopup = %QRWindow
 
 @onready
-var about_window: Control = %AboutWindow
+var about_window: AboutPopup = %AboutWindow
 
 @onready
-var log_window: Control = %Log
+var log_window: LogPopup = %Log
 
 @onready
 var statistic_popup: PopupPanel = $StatisticsPopupPanel

MusicListScrollContainer.gd

@@ -1,3 +1,4 @@
+class_name ScrollToEndContainer
 extends ScrollContainer
 
 var max_value = 0;

MusicPlayer.gd

@@ -25,7 +25,7 @@ var sound_effect_player: AudioStreamPlayer = $AudioSoundEffectPlayer
 var progress_slider: HSlider = $PlayerBar/MusicPlayerContainer/MusicPlayerSlider
 
 @onready
-var volume_slider: HSlider = $PlayerBar/MusicPlayerContainer/VolumeSlider
+var volume_slider: VolumeSlider = $PlayerBar/MusicPlayerContainer/VolumeSlider
 
 @onready
 var music_time_label: Label = $PlayerBar/MusicPlayerContainer/MusicTimeLabel

PlayerNameField.gd

@@ -1,3 +1,4 @@
+class_name PlayerNameField
 extends TextEdit
 
 signal enter_key_pressed

QRWindow.gd

@@ -1,3 +1,4 @@
+class_name QRPopup
 extends PopupWindow
 
 @onready

SearchWindow.gd

@@ -1,3 +1,4 @@
+class_name SearchPopup
 extends PopupWindow
 
 @onready

SettingsWindow.gd

@@ -1,3 +1,4 @@
+class_name SettingsPopup
 extends PopupWindow
 
 @onready

log.gd

@@ -1,3 +1,4 @@
+class_name LogPopup
 extends PopupWindow
 
 @onready

new_character_select.gd

@@ -1,3 +1,4 @@
+class_name CharacterSelectPopup
 extends PopupWindow
 
 @onready

quiz.gd

@@ -33,10 +33,10 @@ var players_panel: PlayersPanel = $PlayersPanel
 var toolbar: QuizToolbar = $QuizToolbar
 
 @onready
-var settings_window: Control = $SettingsWindow
+var settings_window: SettingsPopup = $SettingsWindow
 
 @onready
-var winner_window: Control = %WinnerWindow
+var winner_window: WinnerPopup = %WinnerWindow
 
 @onready
 var song_controls: SongControls = $SongControls
@@ -48,7 +48,7 @@ var song_loader: SongLoader = $SongLoader
 var music_list_panel: MusicListPanel = $MusicListPanel
 
 @onready
-var new_character_select: Control = %NewCharacterSelect
+var new_character_select: CharacterSelectPopup = %NewCharacterSelect
 
 @onready
 var music_player_container: MusicPlayer = $MusicPlayer

shortcuts_window.gd

@@ -1,3 +1,4 @@
+class_name ShortcutsPopup
 extends PopupWindow
 
 @onready

sync_window.gd

@@ -1,3 +1,4 @@
+class_name SyncPopup
 extends PopupWindow
 
 @onready

volume_slider.gd

@@ -1,3 +1,4 @@
+class_name VolumeSlider
 extends HSlider
 
 @export

winner_window.gd

@@ -1,3 +1,4 @@
+class_name WinnerPopup
 extends PopupWindow
 
 @onready