fix: include custom_providers in /model command listings and resolution

Custom providers defined in config.yaml under  were
completely invisible to the /model command in both gateway (Telegram,
Discord, etc.) and CLI. The provider listing skipped them and explicit
switching via --provider failed with "Unknown provider".

Root cause: gateway/run.py, cli.py, and model_switch.py only read the
 dict from config, ignoring  entirely.

Changes:
- providers.py: add resolve_custom_provider() and extend
  resolve_provider_full() to check custom_providers after user_providers
- model_switch.py: propagate custom_providers through switch_model(),
  list_authenticated_providers(), and get_authenticated_provider_slugs();
  add custom provider section to provider listings
- gateway/run.py: read custom_providers from config, pass to all
  model-switch calls
- cli.py: hoist config loading, pass custom_providers to listing and
  switch calls

Tests: 4 new regression tests covering listing, resolution, and gateway
command handler. All 71 tests pass.

hermes_cli/model_switch.py

@@ -336,6 +336,7 @@ def resolve_alias(
 def get_authenticated_provider_slugs(
     current_provider: str = "",
     user_providers: dict = None,
+    custom_providers: list | None = None,
 ) -> list[str]:
     """Return slugs of providers that have credentials.
 
@@ -346,6 +347,7 @@ def get_authenticated_provider_slugs(
         providers = list_authenticated_providers(
             current_provider=current_provider,
             user_providers=user_providers,
+            custom_providers=custom_providers,
             max_models=0,
         )
         return [p["slug"] for p in providers]
@@ -383,6 +385,7 @@ def switch_model(
     is_global: bool = False,
     explicit_provider: str = "",
     user_providers: dict = None,
+    custom_providers: list | None = None,
 ) -> ModelSwitchResult:
     """Core model-switching pipeline shared between CLI and gateway.
 
@@ -416,6 +419,7 @@ def switch_model(
         is_global: Whether to persist the switch.
         explicit_provider: From --provider flag (empty = no explicit provider).
         user_providers: The ``providers:`` dict from config.yaml (for user endpoints).
+        custom_providers: The ``custom_providers:`` list from config.yaml.
 
     Returns:
         ModelSwitchResult with all information the caller needs.
@@ -436,7 +440,11 @@ def switch_model(
     # =================================================================
     if explicit_provider:
         # Resolve the provider
-        pdef = resolve_provider_full(explicit_provider, user_providers)
+        pdef = resolve_provider_full(
+            explicit_provider,
+            user_providers,
+            custom_providers,
+        )
         if pdef is None:
             _switch_err = (
                 f"Unknown provider '{explicit_provider}'. "
@@ -516,6 +524,7 @@ def switch_model(
                 authed = get_authenticated_provider_slugs(
                     current_provider=current_provider,
                     user_providers=user_providers,
+                    custom_providers=custom_providers,
                 )
                 fallback_result = _resolve_alias_fallback(raw_input, authed)
                 if fallback_result is not None:
@@ -590,6 +599,14 @@ def switch_model(
 
     provider_changed = target_provider != current_provider
     provider_label = get_label(target_provider)
+    if target_provider.startswith("custom:"):
+        custom_pdef = resolve_provider_full(
+            target_provider,
+            user_providers,
+            custom_providers,
+        )
+        if custom_pdef is not None:
+            provider_label = custom_pdef.name
 
     # --- Resolve credentials ---
     api_key = current_api_key
@@ -708,6 +725,7 @@ def switch_model(
 def list_authenticated_providers(
     current_provider: str = "",
     user_providers: dict = None,
+    custom_providers: list | None = None,
     max_models: int = 8,
 ) -> List[dict]:
     """Detect which providers have credentials and list their curated models.
@@ -853,6 +871,43 @@ def list_authenticated_providers(
                 "api_url": api_url,
             })
 
+    # --- 4. Saved custom providers from config ---
+    if custom_providers and isinstance(custom_providers, list):
+        for entry in custom_providers:
+            if not isinstance(entry, dict):
+                continue
+
+            display_name = (entry.get("name") or "").strip()
+            api_url = (
+                entry.get("base_url", "")
+                or entry.get("url", "")
+                or entry.get("api", "")
+                or ""
+            ).strip()
+            if not display_name or not api_url:
+                continue
+
+            slug = "custom:" + display_name.lower().replace(" ", "-")
+            if slug in seen_slugs:
+                continue
+
+            models_list = []
+            default_model = (entry.get("model") or "").strip()
+            if default_model:
+                models_list.append(default_model)
+
+            results.append({
+                "slug": slug,
+                "name": display_name,
+                "is_current": slug == current_provider,
+                "is_user_defined": True,
+                "models": models_list,
+                "total_models": len(models_list),
+                "source": "user-config",
+                "api_url": api_url,
+            })
+            seen_slugs.add(slug)
+
     # Sort: current provider first, then by model count descending
     results.sort(key=lambda r: (not r["is_current"], -r["total_models"]))