fix: /model command — bare provider names, custom endpoint display

Two issues with /model preventing proper provider switching:

1. Bare provider names not detected: typing '/model nous' treated 'nous'
   as a model name instead of triggering a provider switch. Fixed by adding
   step 0 in detect_provider_for_model() that checks if the input matches
   a known provider name/alias (excluding 'custom'/'openrouter' which need
   explicit model names) and returns that provider's default model.

2. Custom endpoint details hidden: /model (no args) showed '[custom]' with
   just a usage hint but no endpoint URL or model name. Now displays the
   configured base_url for custom providers in both CLI and gateway.

Note: config base_url and OPENAI_BASE_URL are intentionally NOT cleared on
provider switch — dedicated provider paths (nous, anthropic, codex) have
their own credential resolution that ignores these, and clearing them would
destroy the user's custom endpoint config, preventing switching back.

Co-authored-by: Test <test@test.com>

cli.py

@@ -973,6 +973,8 @@ def save_config_value(key_path: str, value: any) -> bool:
         return False
 
 
+
+
 # ============================================================================
 # HermesCLI Class
 # ============================================================================
@@ -2890,6 +2892,14 @@ class HermesCLI:
                     for mid, desc in curated:
                         current_marker = " ← current" if (is_active and mid == self.model) else ""
                         print(f"      {mid}{current_marker}")
+                elif p["id"] == "custom":
+                    from hermes_cli.models import _get_custom_base_url
+                    custom_url = _get_custom_base_url() or os.getenv("OPENAI_BASE_URL", "")
+                    if custom_url:
+                        print(f"      endpoint: {custom_url}")
+                    if is_active:
+                        print(f"      model: {self.model} ← current")
+                    print(f"      (use /model custom:<model-name>)")
                 else:
                     print(f"      (use /model {p['id']}:<model-name>)")
                 print()