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.

src/gpu_rent/session.py

@@ -22,7 +22,7 @@ from gpu_rent.cloud import (
 )
 from gpu_rent.bootstrap import run_bootstrap
 from gpu_rent.provision import provision_vm, tune_swarm_perf
-from gpu_rent.ready import verify_stack_on_vm, wait_backend_idle
+from gpu_rent.ready import verify_gpu_env, verify_stack_on_vm, wait_backend_idle
 from gpu_rent.snapshot import ensure_boot_snapshot
 from gpu_rent.notify import notify_ready
 from gpu_rent.config import Config
@@ -140,6 +140,18 @@ def _bind_access(
         save_state(state)
         raise
 
+    try:
+        gpu_checks = verify_gpu_env(cfg, ip, log, timeout=600.0)
+        state.notes = dict(state.notes or {})
+        state.notes["gpu_env"] = [
+            {"name": c.name, "ok": c.ok, "detail": c.detail} for c in gpu_checks
+        ]
+    except CloudError as exc:
+        state.notes = dict(state.notes or {})
+        state.notes["gpu_env_error"] = str(exc)[:500]
+        save_state(state)
+        raise
+
     try:
         ensure_boot_snapshot(
             conn,