Use the terminal's own background color

The panes used palette color 0, which color themes such as Catppuccin set
to a grey lighter than their background: everything looked washed out and
grey text almost disappeared (seen in Ghostty on macOS). The startup probe
now also asks for the background color (OSC 11), and with 24-bit color and
a dark background that color is used. The probe always runs at startup, so
a later switch to real images in the Config view never has to ask the
terminal while the screen owns it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019reK4DUGYqDUjniWYJvwUW

internal/ui/app.go

@@ -100,6 +100,9 @@ type overlay struct {
 
 // New builds the application shell: a tab bar, one page per view and a status bar.
 func New(cfg *config.Config) *App {
+	// Ask the terminal before the screen takes it over and before any widget
+	// copies the default background.
+	ownBackground := useTerminalBackground(terminalAnswers(), os.Getenv)
 	a := &App{
 		app:    tview.NewApplication(),
 		tabs:   tview.NewTextView().SetDynamicColors(true),
@@ -136,6 +139,9 @@ func New(cfg *config.Config) *App {
 	if a.covers {
 		a.logs.add(levelInfo, coverNote)
 	}
+	if ownBackground {
+		a.logs.add(levelInfo, "Background: the terminal's own color")
+	}
 	sabClient := sabnzbd.NewClient(cfg.SABnzbd.URL, cfg.SABnzbd.APIKey)
 	a.sab = sabClient
 	a.probes = []probe{