Fix bugs of message disappearing sometimes and being duplicate sometimes

Add message edit and regenerate from any point in conversation

Redesign research subagent display with live stats and rolling steps

feat: beautiful research sub-agent UI with inline progress steps

feat: render cancelled tool state in UI after user interrupt

fix: use backend is_processing as source of truth on refresh

fix: auto-retry on truncated tool calls + correct activity status on refresh

fix: live event streaming after reconnection + LiteLLM timeout

feat: SSE keepalive, reconnection, and is_processing flag

fix: disable chat input during processing after page refresh

fix: per-session state management for smooth task switching

Revert "fix: wire sandbox bash streaming to frontend panel"

fix: wire sandbox bash streaming to frontend panel

stream sandbox creation logs to tool output, fix hf_jobs final status race

replace websocket transport with SSE

feat: resolve sandbox file paths and show tool description in status

fix: approval UI not updating after approve click

feat: per-session WebSocket architecture for parallel chat sessions

feat: cooperative cancellation, session persistence, background generation

feat: implement cooperative agent cancellation with cancel button

feat: merge HF Space improvements