After deleting app/agents/new_chat/, several shared-kernel comments still cited
new_chat paths/cycles. Update the two lazy-import comments in middleware to state
the real reason (tools.registry <-> shared.middleware cycle), and repoint dangling
``new_chat/tools/hitl.py`` / ``chat_deepagent`` doc references to their shared
locations. Comment-only; suite unaffected.
- Added new environment variables for controlling task execution limits, including `SURFSENSE_SUBAGENT_INVOKE_TIMEOUT_SECONDS`, `SURFSENSE_TASK_BATCH_CONCURRENCY`, and `SURFSENSE_TASK_BATCH_MAX_SIZE`.
- Updated documentation to reflect new batch processing capabilities for `task` calls, allowing for concurrent execution of multiple subagent tasks.
- Improved error handling and receipt generation for deliverables, ensuring consistent feedback on task status.
- Refactored middleware to incorporate search space ID for better task management.
