docs: Updated docs to show minimal RAG example and some other minor changes (#1935)

# What does this PR do?
Incorporating some feedback into the docs.

- **`docs/source/getting_started/index.md`:**
    - Demo actually does RAG now
    - Simplified the installation command for dependencies.
    - Updated demo script examples to align with the latest API changes.
- Replaced manual document manipulation with `RAGDocument` for clarity
and maintainability.
- Introduced new logic for model and embedding selection using the Llama
Stack Client SDK.
- Enhanced examples to showcase proper agent initialization and logging.
- **`docs/source/getting_started/detailed_tutorial.md`:**
- Updated the section for listing models to include proper code
formatting with `bash`.
    - Removed and reorganized the "Run the Demos" section for clarity.
- Adjusted tab-item structures and added new instructions for demo
scripts.
- **`docs/_static/css/my_theme.css`:**
- Updated heading styles to include `h2`, `h3`, and `h4` for consistent
font weight.
- Added a new style for `pre` tags to wrap text and break long words,
this is particularly useful for rendering long output from generation.

    
## Test Plan
Tested locally. Screenshot for reference:

<img width="1250" alt="Screenshot 2025-04-10 at 10 12 12 PM"
src="https://github.com/user-attachments/assets/ce1c8986-e072-4c6f-a697-ed0d8fb75b34"
/>

---------

Signed-off-by: Francisco Javier Arceo <farceo@redhat.com>

docs/source/getting_started/detailed_tutorial.md

@@ -173,9 +173,8 @@ You will see the below:
 Done! You can now use the Llama Stack Client CLI with endpoint http://localhost:8321
 ```
 
-#### iii. List Available Models
 List the models
-```
+```bash
 llama-stack-client models list
 Available Models
 
@@ -190,15 +189,6 @@ Available Models
 Total models: 2
 
 ```
-
-## Step 4: Run the Demos
-
-Note that these demos show the [Python Client SDK](../references/python_sdk_reference/index.md).
-Other SDKs are also available, please refer to the [Client SDK](../index.md#client-sdks) list for the complete options.
-
-::::{tab-set}
-
-:::{tab-item} Basic Inference with the CLI
 You can test basic Llama inference completion using the CLI.
 
 ```bash
@@ -221,10 +211,16 @@ ChatCompletionResponse(
     ],
 )
 ```
-:::
 
-:::{tab-item} Basic Inference with a Script
-Alternatively, you can run inference using the Llama Stack client SDK.
+## Step 4: Run the Demos
+
+Note that these demos show the [Python Client SDK](../references/python_sdk_reference/index.md).
+Other SDKs are also available, please refer to the [Client SDK](../index.md#client-sdks) list for the complete options.
+
+::::{tab-set}
+
+:::{tab-item} Basic Inference
+Now you can run inference using the Llama Stack client SDK.
 
 ### i. Create the Script
 Create a file `inference.py` and add the following code:
@@ -269,7 +265,7 @@ Beauty in the bits
 :::
 
 :::{tab-item} Build a Simple Agent
-Now we can move beyond simple inference and build an agent that can perform tasks using the Llama Stack server.
+Next we can move beyond simple inference and build an agent that can perform tasks using the Llama Stack server.
 ### i. Create the Script
 Create a file `agent.py` and add the following code: