Implement GPU environment verification in session management

- Added a new function `verify_gpu_env` to check GPU stack readiness, including nvidia-smi, CUDA, and torch in the Comfy virtual environment when SwarmUI is enabled.
- Updated the session management to call `verify_gpu_env`, capturing GPU environment status and errors in the state notes.
- Enhanced documentation in `cli.md` to reflect the new GPU environment verification process.
- Added tests for `verify_gpu_env` to ensure proper functionality and error handling during GPU checks.

tests/test_verify_stack.py

@@ -1,4 +1,5 @@
-from gpu_rent.ready import ServiceCheck, _expected_services, verify_stack_local
+from gpu_rent.errors import CloudError
+from gpu_rent.ready import ServiceCheck, _expected_services, verify_gpu_env, verify_stack_local
 
 
 class _Cfg:
@@ -41,7 +42,9 @@ def test_verify_stack_local_fails_closed_port(monkeypatch):
         ollama_local_port = 17999
         llamacpp_local_port = 17812
 
-    monkeypatch.setattr("gpu_rent.ready._tcp_ok", lambda port, host="127.0.0.1", timeout=0.8: False)
+    monkeypatch.setattr(
+        "gpu_rent.ready._tcp_ok", lambda port, host="127.0.0.1", timeout=0.8: False
+    )
     logs: list[str] = []
     try:
         verify_stack_local(C(), logs.append, timeout=0.3, poll_every=0.1)
@@ -53,3 +56,86 @@ def test_verify_stack_local_fails_closed_port(monkeypatch):
 def test_service_check_dataclass():
     c = ServiceCheck("x", True, "ok", "vm")
     assert c.ok and c.where == "vm"
+
+
+def test_verify_gpu_env_ok(monkeypatch):
+    payload = {
+        "ok": True,
+        "checks": [
+            {"name": "nvidia-smi", "required": True, "ok": True, "detail": "A100"},
+            {"name": "cuda", "required": True, "ok": True, "detail": "libcuda"},
+            {
+                "name": "torch",
+                "required": True,
+                "ok": True,
+                "detail": "torch=2.0 cuda=12 available=True",
+            },
+            {
+                "name": "triton/sage",
+                "required": False,
+                "ok": True,
+                "detail": "есть: triton; нет: —",
+            },
+        ],
+    }
+
+    def fake_run_python(cfg, host, script, **kw):
+        assert "GPU_RENT_CHECK_SWARM" in script
+        return json.dumps(payload) + "\n"
+
+    import json
+
+    monkeypatch.setattr("gpu_rent.ssh_ops.run_python", fake_run_python)
+    # patch where used
+    monkeypatch.setattr(
+        "gpu_rent.ssh_ops.run_python",
+        fake_run_python,
+        raising=False,
+    )
+
+    import gpu_rent.ready as ready_mod
+
+    monkeypatch.setattr(
+        ready_mod,
+        "run_python",
+        fake_run_python,
+        raising=False,
+    )
+
+    # verify_gpu_env imports run_python inside the function
+    import gpu_rent.ssh_ops as ssh_ops
+
+    monkeypatch.setattr(ssh_ops, "run_python", fake_run_python)
+
+    logs: list[str] = []
+    out = verify_gpu_env(_Cfg(), "1.2.3.4", logs.append, timeout=5.0, poll_every=0.1)
+    assert all(c.ok for c in out)
+    assert any(c.name == "torch" for c in out)
+
+
+def test_verify_gpu_env_fails_without_cuda(monkeypatch):
+    import json
+
+    import gpu_rent.ssh_ops as ssh_ops
+
+    payload = {
+        "ok": False,
+        "checks": [
+            {"name": "nvidia-smi", "required": True, "ok": True, "detail": "ok"},
+            {"name": "cuda", "required": True, "ok": False, "detail": "нет libcuda"},
+            {"name": "torch", "required": True, "ok": False, "detail": "no venv"},
+        ],
+    }
+    monkeypatch.setattr(
+        ssh_ops,
+        "run_python",
+        lambda *a, **k: json.dumps(payload),
+    )
+    logs: list[str] = []
+    try:
+        verify_gpu_env(
+            _Cfg(), "1.2.3.4", logs.append, timeout=0.4, poll_every=0.1
+        )
+        assert False, "expected CloudError"
+    except CloudError as exc:
+        assert "cuda" in str(exc).lower() or "GPU-стек" in str(exc)