Fix message disappearing and duplicate rendering bugs

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