Cloud docs update, Specifying OpenAI dependency, adding explicit instruction for key

docs/get-started/quickstart.mdx

@@ -23,11 +23,18 @@ Let's get you set up with a hello world mcp-agent!
         ```bash
         uvx mcp-agent init
         uv init
-        uv add mcp-agent
+        uv add "mcp-agent[openai]"
         uv sync
         ```
         (Prefer pip? `python -m venv .venv && pip install mcp-agent` works too.)
       </Step>
+      <Step title="Add your model provider key">
+        In the `mcp_agent.secrets.yaml` in your project directory, add your OpenAI or other model provider key.
+        ```yaml mcp_agent.secrets.yaml
+        openai:
+          api_key: "your-openai-api-key"
+        ```
+      </Step>
     </Steps>
   </Tab>
   <Tab title="Do it manually">
@@ -42,7 +49,7 @@ Let's get you set up with a hello world mcp-agent!
       <Step title="Install dependencies with uv">
         ```bash
         uv init
-        uv add mcp-agent
+        uv add "mcp-agent[openai]"
         uv sync
         ```
 
@@ -51,7 +58,7 @@ Let's get you set up with a hello world mcp-agent!
 
       <Step title="Add configuration files">
         `mcp_agent.config.yaml`
-        ```yaml
+        ```yaml mcp_agent.config.yaml
         execution_engine: asyncio
         logger:
           transports: [console]
@@ -71,15 +78,15 @@ Let's get you set up with a hello world mcp-agent!
         ```
 
         `mcp_agent.secrets.yaml`
-        ```yaml
+        ```yaml mcp_agent.secrets.yaml
         openai:
           api_key: "your-openai-api-key"
         ```
       </Step>
 
       <Step title="Paste the hello world agent">
         `main.py`
-        ```python
+        ```python main.py
         import asyncio
         import os
         import time