Library: mark titles that are downloading

While the Library is visible it reads the Radarr and Sonarr queues (on
opening, every 10 s, and shortly after a grab) and matches them to the
titles by movieId / seriesId. Those titles get a blue dot instead of the
green or grey one, and their details say how far the download is.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/ui/help.go

@@ -32,7 +32,7 @@ var helpSections = []helpSection{
 		{"[  ]", "with an empty search box: previous / next Trakt list (trending now, most watched this week, anticipated, popular; movies also the US box office); needs a Trakt client ID (Config view)"},
 		{"r", "reload the Trakt list"},
 	}},
-	{title: "Library", items: []helpItem{
+	{title: "Library", note: "The dot before a title: green when monitored, grey hollow when not, blue while it is in the Radarr/Sonarr download queue (the details say how far).", items: []helpItem{
 		{"Tab", "switch between the movies and series lists"},
 		{"f", "cycle the status filter (all, missing, downloaded, monitored, unmonitored); every list has its own filters"},
 		{"F", "filter by file properties: quality, codec (x265, x264, AV1), HDR / DV / SDR, audio (Atmos, TrueHD, DTS, DD+ ...), language. Changes apply live behind the dialog, also while you move through an open list; Esc undoes them. Options that would leave no results are not offered. Series files are read on demand."},