feat(providers): route gemini through the native AI Studio API

- add a native Gemini adapter over generateContent/streamGenerateContent
- switch the built-in gemini provider off the OpenAI-compatible endpoint
- preserve thought signatures and native functionResponse replay
- route auxiliary Gemini clients through the same adapter
- add focused unit coverage plus native-provider integration checks

hermes_cli/auth.py

@@ -151,7 +151,7 @@ PROVIDER_REGISTRY: Dict[str, ProviderConfig] = {
         id="gemini",
         name="Google AI Studio",
         auth_type="api_key",
-        inference_base_url="https://generativelanguage.googleapis.com/v1beta/openai",
+        inference_base_url="https://generativelanguage.googleapis.com/v1beta",
         api_key_env_vars=("GOOGLE_API_KEY", "GEMINI_API_KEY"),
         base_url_env_var="GEMINI_BASE_URL",
     ),

hermes_cli/models.py

@@ -552,7 +552,7 @@ CANONICAL_PROVIDERS: list[ProviderEntry] = [
     ProviderEntry("copilot",        "GitHub Copilot",           "GitHub Copilot (uses GITHUB_TOKEN or gh auth token)"),
     ProviderEntry("copilot-acp",    "GitHub Copilot ACP",       "GitHub Copilot ACP (spawns `copilot --acp --stdio`)"),
     ProviderEntry("huggingface",    "Hugging Face",             "Hugging Face Inference Providers (20+ open models)"),
-    ProviderEntry("gemini",         "Google AI Studio",         "Google AI Studio (Gemini models — OpenAI-compatible endpoint)"),
+    ProviderEntry("gemini",         "Google AI Studio",         "Google AI Studio (Gemini models — native Gemini API)"),
     ProviderEntry("google-gemini-cli", "Google Gemini (OAuth)",   "Google Gemini via OAuth + Code Assist (free tier supported; no API key needed)"),
     ProviderEntry("deepseek",       "DeepSeek",                 "DeepSeek (DeepSeek-V3, R1, coder — direct API)"),
     ProviderEntry("xai",            "xAI",                      "xAI (Grok models — direct API)"),