Implement headless ComfyUI installation and improve backend status handling

- Added a new function to ensure headless installation of ComfyUI when backends are empty, enhancing the setup process for SwarmUI.
- Updated documentation to clarify the installation flow and backend readiness checks, ensuring users understand the requirements for a successful setup.
- Enhanced backend status checks to differentiate between 'empty' and 'idle' states, improving error handling and user feedback during provisioning.
- Adjusted logging messages to provide clearer insights into the installation and backend status processes.

tests/test_wait_backend_idle.py

@@ -0,0 +1,66 @@
+"""Tests for wait_backend_idle READY semantics and install helpers."""
+
+from gpu_rent.ready import _REMOTE_POLL
+
+
+def test_remote_poll_empty_is_busy_not_ready():
+    assert 'bstat == "empty"' in _REMOTE_POLL
+    assert 'BUSY backend=empty' in _REMOTE_POLL
+    # Must not treat empty as READY anymore
+    assert '("idle", "disabled", "all_disabled", "empty")' not in _REMOTE_POLL
+
+
+def test_remote_poll_idle_is_ready():
+    assert 'bstat == "idle"' in _REMOTE_POLL
+    assert "READY backend=" in _REMOTE_POLL
+
+
+def test_install_swarm_comfy_script_payload():
+    from importlib.resources import files
+
+    text = files("gpu_rent.remote").joinpath("install_swarm_comfy.py").read_text(
+        encoding="utf-8"
+    )
+    assert "InstallConfirmWS" in text
+    assert '"backend": "comfyui"' in text
+    assert '"models": "none"' in text
+    assert "modern_dark" in text
+
+
+def test_verify_gpu_env_fail_fast_empty_dlbackend(monkeypatch):
+    import json
+
+    from gpu_rent.errors import CloudError
+    from gpu_rent.ready import verify_gpu_env
+    import gpu_rent.ssh_ops as ssh_ops
+
+    class Cfg:
+        enable_swarmui = True
+
+    payload = {
+        "ok": False,
+        "checks": [
+            {"name": "nvidia-smi", "required": True, "ok": True, "detail": "ok"},
+            {"name": "cuda", "required": True, "ok": True, "detail": "ok"},
+            {
+                "name": "torch",
+                "required": True,
+                "ok": False,
+                "detail": "ComfyUI venv python не найден (dlbackend пуст — SwarmUI Install не прогоняли)",
+            },
+        ],
+    }
+    calls = {"n": 0}
+
+    def fake(*a, **k):
+        calls["n"] += 1
+        return json.dumps(payload)
+
+    monkeypatch.setattr(ssh_ops, "run_python", fake)
+    logs: list[str] = []
+    try:
+        verify_gpu_env(Cfg(), "1.2.3.4", logs.append, timeout=600.0, poll_every=0.1)
+        assert False, "expected CloudError"
+    except CloudError as exc:
+        assert "fail-fast" in str(exc).lower() or "torch" in str(exc).lower()
+    assert calls["n"] == 1