feat: SSE keepalive, reconnection, and is_processing flag

replace websocket transport with SSE

fix: buffer websocket events during disconnects and replay on reconnect

feat: cleanup sandbox spaces on session end and increase cookie TTL

fix: inject OAuth token into MCP server headers at runtime

fix: route all HF token usage through session.hf_token from OAuth

feat: per-session WebSocket architecture for parallel chat sessions

feat: implement cooperative agent cancellation with cancel button

feat: merge HF Space improvements

format

functioning frontend and docker

Fix config path to use absolute path from project root

Fix session_manager imports - define Operation/Submission locally

Fix imports and add frontend to gitignore

formatting

Add web frontend infrastructure for HF Agent