Fix subtitle-cycle OSD labels and harden quality gates

- Resolve J/Shift+J subtitle-cycle OSD text via track-list labels and property expansion
- Add mpv proxy OSD runtime + regression coverage across IPC/main/runtime paths
- Scope `make pretty` to maintained source files and add scoped Prettier script
- Align release workflow with cache/install order and explicit TypeScript check
- Clean up duplicate submodule entry and remove checked-in docs/plans artifacts

src/main/runtime/ipc-bridge-actions-main-deps.test.ts

@@ -19,6 +19,7 @@ test('ipc bridge action main deps builders map callbacks', async () => {
       playNextSubtitle: () => {},
       shiftSubDelayToAdjacentSubtitle: async () => {},
       sendMpvCommand: () => {},
+      getMpvClient: () => null,
       isMpvConnected: () => true,
       hasRuntimeOptionsManager: () => true,
     }),