Enhance backend management and diagnostics in install_swarm_comfy.py

- Introduced a new `delete_backend` function to facilitate backend removal during recovery processes.
- Improved the `recover_errored_backends` function to handle backend reconfiguration and recreation more effectively, including enhanced logging for diagnostics.
- Added a new `add_comfy_selfstart` function to streamline the addition of new backends.
- Updated the `comfy_start_script` function to prefer absolute paths for better reliability.
- Enhanced diagnostics in `swarm_diag.py` to include detailed backend settings and mount status.
- Added tests to validate the new backend management features and ensure robust error handling.

tests/test_wait_backend_idle.py

@@ -42,8 +42,11 @@ def test_install_swarm_comfy_script_payload():
     assert "sanitize_backends_fds" in text or "recover_empty_backends" in text
     assert "AddNewBackend" in text
     assert "EditBackend" in text
-    assert "dlbackend/ComfyUI/main.py" in text
     assert "configure_comfy_backend" in text
+    assert "ensure_dlbackend_bind" in text
+    assert "DeleteBackend" in text or "delete_backend" in text
+    assert "absolute StartScript" in text or "reconfigure errored" in text
+    assert "/mnt/swarm_data" in text or "DATA /" in text
     assert 'bstat in ("empty", "disabled", "all_disabled", "unknown")' in text