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

docs-site/development.md

@@ -175,9 +175,6 @@ Run `make help` for the full list.
 | `SUBMINER_MPV_PLUGIN_PATH`         | mpv plugin directory the launcher injects                        |
 | `SUBMINER_LOG_LEVEL`               | App log level (`debug`, `info`, `warn`, `error`)                 |
 | `SUBMINER_MPV_LOG`                 | Shared mpv/app log file path                                     |
-| `SUBMINER_JIMAKU_API_KEY`          | Jimaku API key for launcher subtitle downloads                   |
-| `SUBMINER_JIMAKU_API_KEY_COMMAND`  | Command that prints the Jimaku API key                           |
-| `SUBMINER_JIMAKU_API_BASE_URL`     | Jimaku API base URL                                              |
 | `SUBMINER_JELLYFIN_ACCESS_TOKEN`   | Jellyfin access token, used before the stored encrypted session  |
 | `SUBMINER_JELLYFIN_USER_ID`        | Jellyfin user ID                                                 |
 | `SUBMINER_SKIP_MACOS_HELPER_BUILD` | Set to `1` to skip the macOS helper build during `bun run build` |