Show the neoirc-cli screen without waiting at start-up (closes #226)

Run added the start-up status bar and welcome lines through
SetStatus and AddStatus before it started the tview event loop. Both
wait for that loop, so neoirc-cli stopped before it showed its
screen. They now run on a goroutine, as typed lines do.

Run now passes a new UI to run, which holds the start-up path and
returns its error. TestStartUp calls run with a simulation screen. It
fails unless, within five seconds, the status window holds two lines:
first the one with "Welcome to neoirc-cli", then the /connect hint.

Model: opus-5-5

internal/cli/app.go

@@ -34,30 +34,44 @@ type App struct {
 
 // Run creates and runs the CLI application.
 func Run() {
-	app := &App{ //nolint:exhaustruct
-		ui:   NewUI(),
-		nick: "guest",
-	}
-
-	app.ui.OnInput(app.handleInput)
-	app.ui.SetStatus(app.nick, "", "disconnected")
-
-	app.ui.AddStatus(
-		"Welcome to neoirc-cli — an IRC-style client",
-	)
-	app.ui.AddStatus(
-		"Type [yellow]/connect <server-url>" +
-			"[white] to begin, " +
-			"or [yellow]/help[white] for commands",
-	)
-
-	err := app.ui.Run()
+	err := run(NewUI())
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
 		os.Exit(1)
 	}
 }
 
+// run starts the client on ui and returns when ui stops. Tests
+// call it with ui on a simulation screen.
+func run(ui *UI) error {
+	app := &App{ //nolint:exhaustruct
+		ui:   ui,
+		nick: "guest",
+	}
+
+	app.ui.OnInput(app.handleInput)
+
+	// SetStatus and AddStatus wait for the event loop, which
+	// app.ui.Run starts below, so they run on a goroutine. The
+	// nick is read first, as a typed /nick may change app.nick.
+	nick := app.nick
+
+	go func() {
+		app.ui.SetStatus(nick, "", "disconnected")
+
+		app.ui.AddStatus(
+			"Welcome to neoirc-cli — an IRC-style client",
+		)
+		app.ui.AddStatus(
+			"Type [yellow]/connect <server-url>" +
+				"[white] to begin, " +
+				"or [yellow]/help[white] for commands",
+		)
+	}()
+
+	return app.ui.Run()
+}
+
 func (a *App) handleInput(text string) {
 	if strings.HasPrefix(text, "/") {
 		a.handleCommand(text)