fix: model alias fallback uses authenticated providers instead of hardcoded openrouter/nous

When an alias like 'claude' can't be resolved on the current provider,
_resolve_alias_fallback() tries other providers. Previously it hardcoded
('openrouter', 'nous') — so '/model claude' on z.ai would resolve to
openrouter even if the user doesn't have openrouter credentials but does
have anthropic.

Now the fallback uses the user's actual authenticated providers (detected
via list_authenticated_providers which is backed by the models.dev
in-memory cache). If no authenticated providers are found, falls back to
the old ('openrouter', 'nous') for backwards compatibility.

New helper: get_authenticated_provider_slugs() returns just the slug
strings from list_authenticated_providers().

hermes_cli/model_switch.py

@@ -339,12 +339,37 @@ def resolve_alias(
     return None
 
 
+def get_authenticated_provider_slugs(
+    current_provider: str = "",
+    user_providers: dict = None,
+) -> list[str]:
+    """Return slugs of providers that have credentials.
+
+    Uses ``list_authenticated_providers()`` which is backed by the models.dev
+    in-memory cache (1 hr TTL) — no extra network cost.
+    """
+    try:
+        providers = list_authenticated_providers(
+            current_provider=current_provider,
+            user_providers=user_providers,
+            max_models=0,
+        )
+        return [p["slug"] for p in providers]
+    except Exception:
+        return []
+
+
 def _resolve_alias_fallback(
     raw_input: str,
-    fallback_providers: tuple[str, ...] = ("openrouter", "nous"),
+    authenticated_providers: list[str] = (),
 ) -> Optional[tuple[str, str, str]]:
-    """Try to resolve an alias on fallback providers."""
-    for provider in fallback_providers:
+    """Try to resolve an alias on the user's authenticated providers.
+
+    Falls back to ``("openrouter", "nous")`` only when no authenticated
+    providers are supplied (backwards compat for non-interactive callers).
+    """
+    providers = authenticated_providers or ("openrouter", "nous")
+    for provider in providers:
         result = resolve_alias(raw_input, provider)
         if result is not None:
             return result
@@ -494,7 +519,11 @@ def switch_model(
             # --- Step b: Alias exists but not on current provider -> fallback ---
             key = raw_input.strip().lower()
             if key in MODEL_ALIASES:
-                fallback_result = _resolve_alias_fallback(raw_input)
+                authed = get_authenticated_provider_slugs(
+                    current_provider=current_provider,
+                    user_providers=user_providers,
+                )
+                fallback_result = _resolve_alias_fallback(raw_input, authed)
                 if fallback_result is not None:
                     target_provider, new_model, resolved_alias = fallback_result
                     logger.debug(