fix: streaming race — keep Thinking until first token, fall back to JSON when backend doesn't honour stream=true

feat: streaming + multi-turn + view source + doc-scoped + UX fixes

ux: mobile sidebar, stop, rename, hotkeys, sync timestamp + 8 more

feat: persist chat history to backend (debounced PUT, hydrate on mount)

enhance: markdown answers + clean source name suffix

revert: restore Twilight Atelier (drop Risograph Folio)

redesign: Risograph Folio — printed-publication aesthetic

redesign: Twilight Atelier — full chat-app shell