feat(models): swap Gemini catalog entries to 3.1 Pro + 3.6 Flash; drop retired Qwen models

- openrouter + nous curated lists: replace google/gemini-3-pro-preview with
  google/gemini-3.1-pro-preview as the sole Pro entry, and
  google/gemini-3.5-flash with google/gemini-3.6-flash
- remove qwen/qwen3.7-plus and qwen/qwen3.6-35b-a3b from both lists
- regenerate website/static/api/model-catalog.json
- test fixture: swap qwen3.7-plus catalog-label fixture to qwen3.7-max
  (must be a model present in the nous curated list)

Both new Gemini ids verified live on OpenRouter /api/v1/models and the
Nous portal /v1/models (1,048,576 ctx — covered by the existing 'gemini'
prefix in DEFAULT_CONTEXT_LENGTHS).

tests/test_empty_model_fallback.py

@@ -74,16 +74,16 @@ class TestGetDefaultModelForProvider:
 
         with patch(
             "hermes_cli.model_catalog.get_default_model_from_cache",
-            return_value="qwen/qwen3.7-plus",
+            return_value="qwen/qwen3.7-max",
         ):
             assert (
                 models_mod.get_preferred_silent_default_model("nous")
-                == "qwen/qwen3.7-plus"
+                == "qwen/qwen3.7-max"
             )
-            # nous catalog carries qwen3.7-plus, so the full resolver follows.
+            # nous catalog carries qwen3.7-max, so the full resolver follows.
             assert (
                 models_mod.get_default_model_for_provider("nous")
-                == "qwen/qwen3.7-plus"
+                == "qwen/qwen3.7-max"
             )
 
     def test_no_catalog_cache_falls_back_to_constant(self):