feat: enhance task management and timeout configurations in multi-agent chat

- 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.

surfsense_backend/app/tasks/chat/streaming/handlers/tools/deliverables/generate_video_presentation/emission.py

@@ -15,12 +15,24 @@ def iter_completion_emission_frames(
     out = ctx.tool_output
     payload = out if isinstance(out, dict) else {"result": out}
     yield ctx.emit_tool_output_card(payload)
-    if isinstance(out, dict) and out.get("status") == "pending":
+    if not isinstance(out, dict):
+        return
+    status = out.get("status")
+    # ``ready`` is the live success status now that the tool waits for the
+    # Celery worker to reach a terminal state. ``pending`` is retained as a
+    # legacy branch for old saved chats that pre-date the wait-for-terminal
+    # change (see ``app.agents.shared.deliverable_wait``).
+    if status == "ready":
+        yield ctx.streaming_service.format_terminal_info(
+            f"Video presentation generated successfully: {out.get('title', 'Presentation')}",
+            "success",
+        )
+    elif status == "pending":
         yield ctx.streaming_service.format_terminal_info(
             f"Video presentation queued: {out.get('title', 'Presentation')}",
             "success",
         )
-    elif isinstance(out, dict) and out.get("status") == "failed":
+    elif status == "failed":
         error_msg = out.get("error", "Unknown error")
         yield ctx.streaming_service.format_terminal_info(
             f"Presentation generation failed: {error_msg}",