Loading indicators: the braille spinner now carries a contextual label
(Refreshing…, Fetching…, Loading more…, Discovering…, Searching…) and is
shown in every loading state that previously rendered nothing — Discover
results, Search results fallback, and the empty Feed list.
Feed pagination: a focusable "[Fetch More]" row at the bottom of the flat
feed list advances every feed's loaded window by 50 episodes via the new
loadMoreAllFeeds/hasMoreAcrossAll store API. Behavior is a setting
(Fetch More: manual|auto, default manual) persisted in config.json; auto
fetches when focus reaches the bottom row. The button row is excluded
from episode focus so no episode is double-highlighted while it is active.
