Keep the connection state in the status bar on /window (closes #225)

/window set the status bar to [connected] whatever the connection
state, and Alt and a digit runs /window. Before /connect, both made
the status bar say [connected] while the client had no session.

/window now reads the connection state with the nick and shows
[connected] only while the client is connected, [disconnected]
otherwise. TestWindowConnectionState types /window 0 and presses
Alt and 0, connected and not, and checks the status bar.

Model: opus-5-5

internal/cli/app_internal_test.go

@@ -297,6 +297,69 @@ func TestAltDigit(t *testing.T) {
 	}
 }
 
+// TestWindowConnectionState checks that typing /window 0, or
+// pressing Alt and 0, leaves the status bar showing [connected]
+// only while the client is connected, and [disconnected] otherwise.
+func TestWindowConnectionState(t *testing.T) {
+	t.Parallel()
+
+	const line = "/window 0"
+
+	typeLine := func(ui *UI) {
+		for _, r := range line {
+			ui.app.QueueEvent(tcell.NewEventKey(tcell.KeyRune, r, tcell.ModNone))
+		}
+
+		ui.app.QueueEvent(tcell.NewEventKey(tcell.KeyEnter, 0, tcell.ModNone))
+	}
+
+	pressAltZero := func(ui *UI) {
+		ui.app.QueueEvent(tcell.NewEventKey(tcell.KeyRune, '0', tcell.ModAlt))
+	}
+
+	tests := []struct {
+		name      string
+		send      func(ui *UI)
+		connected bool
+		want      string
+	}{
+		{
+			name: "typed line, not connected", send: typeLine,
+			connected: false, want: "[disconnected]",
+		},
+		{
+			name: "Alt and 0, not connected", send: pressAltZero,
+			connected: false, want: "[disconnected]",
+		},
+		{
+			name: "typed line, connected", send: typeLine,
+			connected: true, want: "[connected]",
+		},
+		{
+			name: "Alt and 0, connected", send: pressAltZero,
+			connected: true, want: "[connected]",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+
+			app := &App{ui: NewUI(), nick: testNick, connected: test.connected}
+			handled := handledLines(app)
+			runUI(t, app.ui)
+
+			test.send(app.ui)
+			waitHandled(t, handled, line)
+
+			status := statusBarText(app.ui)
+			if !strings.Contains(status, test.want) {
+				t.Fatalf("status bar is %q, want it to show %s", status, test.want)
+			}
+		})
+	}
+}
+
 // TestEventLoopKeepsRunning sends Alt and 1, then a typed line and
 // Enter, to a running UI. It checks that both are handled, so the
 // event loop did not stop on either.