Subscribe to a zombie's live activity stream (SSE)

Server-Sent Events tail of the Redis pub/sub channel zombie:{id}:activity. The handler SUBSCRIBEs on a dedicated Redis connection and forwards each PUBLISH frame as one SSE event with id (per-connection monotonic counter), event (frame kind), and data (JSON payload) lines. Frame kinds - event_received, tool_call_started, tool_call_progress, chunk, tool_call_completed, event_complete. Sequence ids reset to 0 on every new SUBSCRIBE and the server ignores Last-Event-ID. Clients reconnect by calling GET /events with a cursor to backfill the durable record, then re-open this stream. Authentication this slice is Bearer-only (CLI / programmatic). Browser cookie auth lands with the dashboard slice.