feat(demo): full showcase polish - mouse cursor, robust selection, HF affiliations

fix(ui,publisher): kill theme/color flickers and translation prompts

feat(editor): embed studio with data files and agent-aware editing

feat(frontend): editor refresh (embed studio, comment popover, shiki, top bar, hooks, styles)

feat: show real HF username and avatar for connected users

fix: resolve TipTap v3 collaboration crash

refactor: store pre-computed attrs in citation/bibliography nodes

chore: initial commit