fix: clarify when OpenAI API key is vs isn't needed

Add info box to quick_start.md explaining that UiPathChatOpenAI
handles auth via UiPath LLM Gateway (no key needed), but direct
OpenAI client usage requires OPENAI_API_KEY. Revert rag-assistant
.env.example since that sample uses the OpenAI client directly.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: cosmyo

packages/uipath-openai-agents/docs/quick_start.md

@@ -12,6 +12,10 @@ Before proceeding, ensure you have the following installed:
 -   `pip` or `uv` package manager
 -   A UiPath Automation Cloud account with appropriate permissions
 
+/// info
+The generated boilerplate uses `UiPathChatOpenAI`, which routes all LLM requests through the **UiPath LLM Gateway**. No OpenAI API key is required — authentication is handled via `uipath auth`. If you choose to use the OpenAI client directly (without `UiPathChatOpenAI`), you will need to configure an `OPENAI_API_KEY` environment variable.
+///
+
 ## Creating a New Project
 
 We recommend using `uv` for package management. To create a new project:

packages/uipath-openai-agents/samples/rag-assistant/.env.example

@@ -1,3 +1,4 @@
-# UiPath Configuration
-# No OpenAI API key is needed - UiPathChatOpenAI routes requests through UiPath's LLM Gateway.
-# Run `uipath auth` to authenticate with UiPath Automation Cloud.
+# This sample uses the OpenAI client directly (without UiPathChatOpenAI),
+# so an OpenAI API key is required.
+# Get your API key from https://platform.openai.com/api-keys
+OPENAI_API_KEY=sk-...