- Extract remaining runtime helper clusters from main.ts into dedicated modules for readability:\n - src/main/jlpt-runtime.ts\n - src/main/media-runtime.ts\n - src/main/overlay-visibility-runtime.ts\n- Wire main.ts to use the new runtime services and remove duplicated in-file helpers.\n- Preserve existing behavior via full typecheck + test:fast verification.\n- Finalize and archive TASK-56 backlog entry; update TASK-54 with completion metadata and summary.
