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/core/services/subtitle-cue-parser.test.ts

@@ -1,7 +1,6 @@
 import assert from 'node:assert/strict';
 import test from 'node:test';
 import { parseSrtCues, parseAssCues, parseSubtitleCues } from './subtitle-cue-parser';
-import type { SubtitleCue } from '../../types';
 
 test('parseSrtCues parses basic SRT content', () => {
   const content = [