Refactor backend status handling and improve idle management

- Updated the idle-killer logic to treat SwarmUI `empty` and `disabled` states as busy, preventing unnecessary idle time during provisioning.
- Enhanced the `wait_backend_idle` function to recognize suspended backends as ready, improving resource utilization and user feedback.
- Refined the `install_swarm_comfy` script to skip installation when backends are already present, streamlining the setup process.
- Improved the `resolve_llm_runtime` function to prioritize live configuration over stale state notes, ensuring accurate runtime detection.
- Added tests to validate the new backend status handling and idle management logic, ensuring robustness and reliability.

src/gpu_rent/access_card.py

@@ -25,17 +25,8 @@ class AccessLink:
 
 
 def resolve_llm_runtime(cfg: Config) -> str:
-    """Live config wins; notes only if cfg is none (legacy session hint)."""
-    runtime = normalize_runtime(cfg.llm_runtime)
-    if runtime != "none":
-        return runtime
-    try:
-        noted = (load_state().notes or {}).get("llm_runtime")
-        if noted:
-            return normalize_runtime(str(noted))
-    except Exception:
-        pass
-    return "none"
+    """Same source as tunnel_forwards: live cfg only (not stale state notes)."""
+    return normalize_runtime(getattr(cfg, "llm_runtime", "none"))
 
 
 def collect_access_links(cfg: Config, *, tunneled: bool) -> list[AccessLink]: