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

.github/workflows/release.yml

@@ -31,9 +31,6 @@ jobs:
         with:
           node-version: 22.12.0
 
-      - name: Install dependencies
-        run: bun install --frozen-lockfile
-
       - name: Cache dependencies
         uses: actions/cache@v4
         with:
@@ -48,6 +45,9 @@ jobs:
       - name: Install dependencies
         run: bun install --frozen-lockfile
 
+      - name: Build (TypeScript check)
+        run: bun run typecheck
+
       - name: Test suite (source)
         run: bun run test:fast