feat(config): unify mpv plugin options under main config and add CSS/Ani

- Replace subminer.conf plugin config with mpv.* fields in config.jsonc
- Add socketPath, backend, autoStartSubMiner, pauseUntilOverlayReady, aniskipEnabled/buttonKey, subminerBinaryPath to mpv config
- Add subtitleSidebar.css field; migrate legacy sidebar appearance fields
- Add paintOrder and WebkitTextStroke to subtitle style options
- Update default subtitle/sidebar fontFamily to CJK-first stack
- Fix overlay visible state surviving mpv y-r restart
- Fix live config saves applying subtitle CSS immediately to open overlays
- Migrate legacy primary/secondary subtitle appearance into subtitleStyle.css on load
- Switch AniSkip button key setting to click-to-learn key capture

src/types/settings.ts

@@ -4,7 +4,6 @@ export type ConfigSettingsCategory =
   | 'appearance'
   | 'behavior'
   | 'mining-anki'
-  | 'playback-sources'
   | 'input'
   | 'integrations'
   | 'tracking-app'
@@ -22,6 +21,7 @@ export type ConfigSettingsControl =
   | 'secret'
   | 'keyboard-shortcut'
   | 'key-code'
+  | 'mpv-key'
   | 'known-words-decks'
   | 'anki-note-type'
   | 'anki-field'