Add coding agent with GPT-5.1 cookbook guide (#2238)

Author: katia-openai

.gitignore

@@ -138,6 +138,7 @@ dmypy.json
 tmp_*
 examples/fine-tuned_qa/local_cache/*
 examples/multimodal/.local_cache/*
+examples/coding-agent-workspace
 
 # PyCharm files
 .idea/