fix: use placeholder api_key for custom providers without credentials (#3604)

Local/custom OpenAI-compatible providers (Ollama, LM Studio, vLLM) that
don't require auth were hitting empty api_key rejections from the OpenAI
SDK, especially when used as smart model routing targets.

Uses the same 'no-key-required' placeholder already used in
_resolve_openrouter_runtime() for the identical scenario.


Salvaged from PR #3543.

Co-authored-by: scottlowry <scottlowry@users.noreply.github.com>

hermes_cli/runtime_provider.py

@@ -203,7 +203,7 @@ def _resolve_named_custom_runtime(
         or _detect_api_mode_for_url(base_url)
         or "chat_completions",
         "base_url": base_url,
-        "api_key": api_key,
+        "api_key": api_key or "no-key-required",
         "source": f"custom_provider:{custom_provider.get('name', requested_provider)}",
     }