feat(myshows): add Fetch More row to per-show episode lists

Mirrors the Feed tab's '[Fetch More]' row inside a drilled show's episode
list (My Shows depth 1): shows only while the show's cache holds episodes
beyond its loaded window, and advances just that show's window by 50 on
Enter (or automatically at the bottom in auto mode). Same fetchMoreMode
preference drives both behaviors. Adds a store-contract test for the
per-feed pagination path.

src/types/settings.ts

@@ -86,7 +86,7 @@ export type AppSettings = {
 	visualizer: VisualizerSettings;
 };
 
-/** How the Feed list loads older episodes (default: manual "[Fetch More]"). */
+/** How the Feed and per-show episode lists load older episodes (default: manual "[Fetch More]"). */
 export type FetchMoreMode = "manual" | "auto";
 
 /** Which shows the auto-download setting applies to (default: all). */