VSH: Insert and eject UMDs from the pause screen

While the XMB is running, the pause screen offers "Insert UMD" with the
drive empty, opening the Switch UMD game picker, and "Eject UMD" with a disc
in. The XMB notices the change through its drive callback, as it does over
the debugger's game.umd.insert/eject. Games keep "Switch UMD".

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

UI/MainScreen.cpp

@@ -906,7 +906,7 @@ void UmdReplaceScreen::CreateViews() {
 		rightColumnItems->Add(new Choice(mm->T("Load", "Load...")))->OnClick.Add([&](UI::EventParams &e) {
 			auto mm = GetI18NCategory(I18NCat::MAINMENU);
 			System_BrowseForFile(GetRequesterToken(), mm->T("Load"), BrowseFileType::BOOTABLE, [this](std::string_view value, int) {
-				__UmdReplace(Path(value));
+				UseDisc(Path(value));
 				TriggerFinish(DR_OK);
 			});
 		});
@@ -933,10 +933,21 @@ void UmdReplaceScreen::update() {
 }
 
 void UmdReplaceScreen::OnGameSelected(UI::EventParams &e) {
-	__UmdReplace(Path(e.s));
+	UseDisc(Path(e.s));
 	TriggerFinish(DR_OK);
 }
 
+void UmdReplaceScreen::UseDisc(const Path &path) {
+	if (!insert_) {
+		__UmdReplace(path);
+		return;
+	}
+	std::string error;
+	if (!__UmdInsert(path, &error)) {
+		g_OSD.Show(OSDType::MESSAGE_ERROR, error);
+	}
+}
+
 void UmdReplaceScreen::OnGameSettings(UI::EventParams &e) {
 	screenManager()->push(new GameSettingsScreen(Path()));
 }