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

Makefile

@@ -98,7 +98,7 @@ ensure-bun:
 	@command -v bun >/dev/null 2>&1 || { printf '%s\n' "[ERROR] bun not found"; exit 1; }
 
 pretty: ensure-bun
-	@bun run format
+	@bun run format:src
 
 build:
 	@printf '%s\n' "[INFO] Detected platform: $(PLATFORM)"