feat(gemini): improve request context for support and compatibility

Include the Hermes client name and version with Gemini inference, model and tier checks, and TTS requests. Add focused coverage for the request headers and keep the Gemini-specific context scoped to Google Gemini endpoints.

tools/tts_tool.py

@@ -1850,11 +1850,24 @@ def _generate_gemini_tts(text: str, output_path: str, tts_config: Dict[str, Any]
         },
     }
 
+    try:
+        import hermes_cli as _hermes_cli
+
+        _hermes_version = str(_hermes_cli.__version__)
+    except Exception:
+        _hermes_version = "0.0.0"
+
     endpoint = f"{base_url}/models/{model}:generateContent"
     response = requests.post(
         endpoint,
         params={"key": api_key},
-        headers={"Content-Type": "application/json"},
+        headers={
+            "Content-Type": "application/json",
+            # Include Hermes client context following Gemini's partner
+            # integration guidance:
+            # https://ai.google.dev/gemini-api/docs/partner-integration
+            "X-Goog-Api-Client": f"hermes-agent/{_hermes_version}",
+        },
         json=payload,
         timeout=60,
     )