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/configapply.go

@@ -35,6 +35,9 @@ func (a *App) applyConfig(c *config.Config) {
 		a.downloads.setInterval(time.Duration(c.UI.RefreshSeconds) * time.Second)
 	}
 	a.bell = c.UI.Bell
+	if old.UI.Theme != c.UI.Theme {
+		a.setTheme(chooseTheme(c.UI.Theme, terminalAnswers()))
+	}
 	if c.UI.ShouldNotifyDownloads() != a.notifyDone {
 		a.setNotifyDownloads(c.UI.ShouldNotifyDownloads())
 	}