- routes/op.ts: editor / upload / youtube-start reject when folder.parentId === null
- op/folder.ejs: at depth 1 show only "하위 폴더 추가"; at depth 2 show
"영상 추가" + "플레이리스트 추가". Video grid and sub-folder modal
rendered conditionally.
- folder.ejs (public): at depth 1 render only sub-folder grid; at depth 2
render only video grid.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>