feat: Issue #42 - Integrate Nexus Architect tools into Hermes

- Add tools.nexus_architect to _discover_tools() in model_tools.py
- Add nexus_architect toolset to toolsets.py with 6 tools:
  - nexus_design_room
  - nexus_create_portal
  - nexus_add_lighting
  - nexus_validate_scene
  - nexus_export_scene
  - nexus_get_summary

The Nexus Architect tool enables autonomous 3D world generation
for the Three.js Nexus environment. Tools are now discoverable
and usable through the Hermes tool system.

model_tools.py

@@ -196,6 +196,7 @@ def _discover_tools():
             "tools.send_message_tool",
             "tools.honcho_tools",
             "tools.homeassistant_tool",
+            "tools.nexus_architect",
         ]
         import importlib
         for mod_name in _modules:

toolsets.py

@@ -208,6 +208,12 @@ TOOLSETS = {
         "includes": []
     },
 
+    "nexus_architect": {
+        "description": "Autonomous 3D world generation for Three.js Nexus",
+        "tools": ["nexus_design_room", "nexus_create_portal", "nexus_add_lighting", "nexus_validate_scene", "nexus_export_scene", "nexus_get_summary"],
+        "includes": []
+    },
+
 
     # Scenario-specific toolsets