Add o3-pro model support and extend test coverage

- Added o3-pro model configuration to custom_models.json with 200K context
- Updated OpenAI provider to support o3-pro with fixed temperature constraint
- Extended simulator tests to include o3-pro validation scenarios

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

conf/custom_models.json

@@ -148,6 +148,15 @@
       "supports_function_calling": true,
       "description": "OpenAI's o3-mini with high reasoning effort - optimized for complex problems"
     },
+    {
+      "model_name": "openai/o3-pro",
+      "aliases": ["o3-pro", "o3pro"],
+      "context_window": 200000,
+      "supports_extended_thinking": false,
+      "supports_json_mode": true,
+      "supports_function_calling": true,
+      "description": "OpenAI's o3-pro model - professional-grade reasoning and analysis"
+    },
     {
       "model_name": "openai/o4-mini",
       "aliases": ["o4-mini", "o4mini"],