fix(auth): stop silently falling back to OpenRouter when no provider is configured (#3862)

Previously, when no API keys or provider credentials were found, Hermes
silently defaulted to OpenRouter + Claude Opus. This caused confusion
when users configured local servers (LM Studio, Ollama, etc.) with a
typo or unrecognized provider name — the system would silently route to
OpenRouter instead of telling them something was wrong.

Changes:
- resolve_provider() now raises AuthError when no credentials are found
  instead of returning 'openrouter' as a silent fallback
- Added local server aliases: lmstudio, ollama, vllm, llamacpp → custom
- Removed hardcoded 'anthropic/claude-opus-4.6' fallback from gateway
  and cron scheduler (they read from config.yaml instead)
- Updated cli-config.yaml.example with complete provider documentation
  including all supported providers, aliases, and local server setup

cron/scheduler.py

@@ -321,7 +321,7 @@ def run_job(job: dict) -> tuple[bool, str, str, Optional[str]]:
             if delivery_target.get("thread_id") is not None:
                 os.environ["HERMES_CRON_AUTO_DELIVER_THREAD_ID"] = str(delivery_target["thread_id"])
 
-        model = job.get("model") or os.getenv("HERMES_MODEL") or "anthropic/claude-opus-4.6"
+        model = job.get("model") or os.getenv("HERMES_MODEL") or ""
 
         # Load config.yaml for model, reasoning, prefill, toolsets, provider routing
         _cfg = {}