Switch the theme live

Widgets copy their colors when they are created, so they now get role
tokens (one unique RGB value per role) instead of colors, and a wrapper
around the tcell screen replaces the tokens with the current theme's
colors in SetContent. Changing the theme in the Config view swaps that
table; the next draw recolors everything. Poster colors that equal a
token are nudged off it.

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

internal/ui/app.go

@@ -30,6 +30,8 @@ type view struct {
 // App is the top-level arr-tui application.
 type App struct {
 	app    *tview.Application
+	theme  theme         // the colors in use
+	themed *themedScreen // draws with them; nil until Run
 	tabs   *tview.TextView
 	pages  *tview.Pages
 	status *tview.TextView
@@ -103,7 +105,7 @@ func New(cfg *config.Config) *App {
 	// Ask the terminal before the screen takes it over, and set the colors
 	// before any widget copies them.
 	th, themeNote := chooseTheme(cfg.UI.Theme, terminalAnswers())
-	th.apply()
+	useTokens()
 	a := &App{
 		app:    tview.NewApplication(),
 		tabs:   tview.NewTextView().SetDynamicColors(true),
@@ -140,6 +142,7 @@ func New(cfg *config.Config) *App {
 	if a.covers {
 		a.logs.add(levelInfo, coverNote)
 	}
+	a.theme = th
 	a.logs.add(levelInfo, themeNote)
 	sabClient := sabnzbd.NewClient(cfg.SABnzbd.URL, cfg.SABnzbd.APIKey)
 	a.sab = sabClient
@@ -394,12 +397,34 @@ func (a *App) Run() error {
 			a.gfx.deleteAll()
 		}
 	}()
+	// The screen draws through the theme (see themedScreen).
+	s, err := tcell.NewScreen()
+	if err != nil {
+		return err
+	}
+	a.themed = newThemedScreen(s, a.theme)
+	a.app.SetScreen(a.themed) // initializes it
+	if a.themed.initErr != nil {
+		return a.themed.initErr
+	}
+	a.themed.DisableMouse()
+	a.themed.DisablePaste()
+
 	go a.watchServices(stop)
 	a.setNotifyDownloads(a.notifyDone)
 	defer a.setNotifyDownloads(false)
 	return a.app.Run()
 }
 
+// setTheme switches the colors while the program runs.
+func (a *App) setTheme(t theme, note string) {
+	a.theme = t
+	if a.themed != nil {
+		a.themed.setTheme(t)
+	}
+	a.logs.add(levelInfo, note)
+}
+
 // setNotifyDownloads starts or stops the background watch for finished downloads.
 func (a *App) setNotifyDownloads(on bool) {
 	a.notifyDone = on