Improve first-launch profile config UX

see a351dcc

src/BizHawk.Client.Common/DisplayManager/OSDManager.cs

@@ -83,6 +83,10 @@ private string MakeFrameCounter()
 		private readonly List<UIDisplay> _guiTextList = [ ];
 		private readonly List<UIDisplay> _ramWatchList = [ ];
 
+		/// <summary>Clears the queue used by <see cref="AddMessage"/>. You probably don't want to do this.</summary>
+		public void ClearRegularMessages()
+			=> _messages.Clear();
+
 		public void AddMessage(string message, int? duration = null)
 			=> _messages.Add(new() {
 				Message = message,

src/BizHawk.Client.EmuHawk/MainForm.Events.cs

@@ -1514,12 +1514,13 @@ private void FreezeStatus_Click(object sender, EventArgs e)
 
 		private void ProfileFirstBootLabel_Click(object sender, EventArgs e)
 		{
-			// We do not check if the user is actually setting a profile here.
-			// This is intentional.
 			using var profileForm = new ProfileConfig(Config, this);
-			this.ShowDialogWithTempMute(profileForm);
+			_ = this.ShowDialogWithTempMute(profileForm); // interpret Cancel as user acklowledgement (there are instructions for re-opening the dialog anyway)
 			Config.FirstBoot = false;
 			ProfileFirstBootLabel.Visible = false;
+			OSD.ClearRegularMessages();
+			AddOnScreenMessage("You can find that again at Config > Profiles", duration: 10/*seconds*/); // intentionally left off the ellipsis from the menu item's name as it could be misinterpreted as the message being truncated
+			AddOnScreenMessage("All done! Drag+drop a rom to start playing", duration: 10/*seconds*/);
 		}
 
 		private void LinkConnectStatusBarButton_Click(object sender, EventArgs e)