fix: show custom endpoint models in /model via live API probe (#1645)

Add 'custom' to the provider order so custom OpenAI-compatible
endpoints appear in /model list. Probes the endpoint's /models API
to dynamically discover available models.

Changes:
- Add 'custom' to _PROVIDER_ORDER in list_available_providers()
- Add _get_custom_base_url() helper to read model.base_url from config
- Add custom branch in provider_model_ids() using fetch_api_models()
- Custom endpoint detection via base_url presence for has_creds check

Based on PR #1612 by @aashizpoudel.

Co-authored-by: Aashish Poudel <aashizpoudel@users.noreply.github.com>

hermes_cli/models.py

@@ -162,7 +162,7 @@ def list_available_providers() -> list[dict[str, str]]:
     _PROVIDER_ORDER = [
         "openrouter", "nous", "openai-codex",
         "zai", "kimi-coding", "minimax", "minimax-cn", "anthropic",
-        "ai-gateway", "deepseek",
+        "ai-gateway", "deepseek", "custom",
     ]
     # Build reverse alias map
     aliases_for: dict[str, list[str]] = {}
@@ -176,9 +176,12 @@ def list_available_providers() -> list[dict[str, str]]:
         # Check if this provider has credentials available
         has_creds = False
         try:
-            from hermes_cli.runtime_provider import resolve_runtime_provider
-            runtime = resolve_runtime_provider(requested=pid)
-            has_creds = bool(runtime.get("api_key"))
+            if pid == "custom":
+                has_creds = bool(_get_custom_base_url())
+            else:
+                from hermes_cli.runtime_provider import resolve_runtime_provider
+                runtime = resolve_runtime_provider(requested=pid)
+                has_creds = bool(runtime.get("api_key"))
         except Exception:
             pass
         result.append({
@@ -217,6 +220,19 @@ def parse_model_input(raw: str, current_provider: str) -> tuple[str, str]:
     return (current_provider, stripped)
 
 
+def _get_custom_base_url() -> str:
+    """Get the custom endpoint base_url from config.yaml."""
+    try:
+        from hermes_cli.config import load_config
+        config = load_config()
+        model_cfg = config.get("model", {})
+        if isinstance(model_cfg, dict):
+            return str(model_cfg.get("base_url", "")).strip()
+    except Exception:
+        pass
+    return ""
+
+
 def curated_models_for_provider(provider: Optional[str]) -> list[tuple[str, str]]:
     """Return ``(model_id, description)`` tuples for a provider's model list.
 
@@ -396,6 +412,18 @@ def provider_model_ids(provider: Optional[str]) -> list[str]:
         live = _fetch_ai_gateway_models()
         if live:
             return live
+    if normalized == "custom":
+        base_url = _get_custom_base_url()
+        if base_url:
+            # Try common API key env vars for custom endpoints
+            api_key = (
+                os.getenv("CUSTOM_API_KEY", "")
+                or os.getenv("OPENAI_API_KEY", "")
+                or os.getenv("OPENROUTER_API_KEY", "")
+            )
+            live = fetch_api_models(api_key, base_url)
+            if live:
+                return live
     return list(_PROVIDER_MODELS.get(normalized, []))