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

tests/test_api_key_providers.py

@@ -266,7 +266,8 @@ class TestResolveProvider:
 
     def test_auto_does_not_select_copilot_from_github_token(self, monkeypatch):
         monkeypatch.setenv("GITHUB_TOKEN", "gh-test-token")
-        assert resolve_provider("auto") == "openrouter"
+        with pytest.raises(AuthError, match="No inference provider configured"):
+            resolve_provider("auto")
 
 
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