refactor: remove dead code and enable noUnusedLocals (#292)

* refactor: remove dead code and enable noUnusedLocals

- delete launcher/jimaku.ts and the launcher Args/config jimaku* fields
  that only fed it (the SUBMINER_JIMAKU_* env vars had no effect)
- delete plugin/subminer/hover.lua; nothing has sent subminer-hover-token
  since Overlay 2.0
- drop never-read anilist.characterDictionary.refreshTtlHours and
  evictionPolicy (still hidden in the settings UI for old configs)
- drop unused root deps: eslint, @fontsource-variable/geist{,-mono}
  (stats/ declares its own)
- delete the committed draft renderer-performance plan doc
- turn on noUnusedLocals for typecheck and remove what it surfaced,
  including Windows focus-handoff values computed but never consumed

* docs(changes): add docs fragment and note retired hover messages

src/renderer/modals/youtube-track-picker.ts

@@ -31,12 +31,6 @@ export function createYoutubeTrackPickerModal(
     ctx.dom.youtubePickerStatus.style.color = isError ? '#ed8796' : '#a5adcb';
   }
 
-  function getTrackLabel(trackId: string): string {
-    return (
-      ctx.state.youtubePickerPayload?.tracks.find((track) => track.id === trackId)?.label ?? ''
-    );
-  }
-
   function renderTrackList(): void {
     ctx.dom.youtubePickerTracks.replaceChildren();
     const payload = ctx.state.youtubePickerPayload;