docs: Reorganize documentation on the webpage (#2651)

# What does this PR do?
Reorganizes the Llama stack webpage into more concise index pages,
introduce more of a workflow, and reduce repetition of content.

New nav structure so far based on #2637 

Further discussions in
https://github.com/meta-llama/llama-stack/discussions/2585

**Preview:**
![Screenshot 2025-07-09 at 2 31
53 PM](https://github.com/user-attachments/assets/4c1f3845-b328-4f12-9f20-3f09375007af)

You can also build a full local preview locally 

 **Feedback**
Looking for feedback on page titles and general feedback on the new
structure

**Follow up documentation**
I plan on reducing some sections and standardizing some terminology in a
follow up PR.
More discussions on that in
https://github.com/meta-llama/llama-stack/discussions/2585

docs/source/providers/index.md

@@ -1,4 +1,4 @@
-# Providers Overview
+# API Providers Overview
 
 The goal of Llama Stack is to build an ecosystem where users can easily swap out different implementations for the same API. Examples for these include:
 - LLM inference providers (e.g., Meta Reference, Ollama, Fireworks, Together, AWS Bedrock, Groq, Cerebras, SambaNova, vLLM, OpenAI, Anthropic, Gemini, WatsonX, etc.),
@@ -13,13 +13,25 @@ Providers come in two flavors:
 Importantly, Llama Stack always strives to provide at least one fully inline provider for each API so you can iterate on a fully featured environment locally.
 
 ## External Providers
-
 Llama Stack supports external providers that live outside of the main codebase. This allows you to create and maintain your own providers independently.
 
 ```{toctree}
 :maxdepth: 1
 
-external
+external.md
+```
+
+```{include} openai.md
+:start-after: ## OpenAI API Compatibility
+```
+
+## Inference
+Runs inference with an LLM.
+
+```{toctree}
+:maxdepth: 1
+
+inference/index
 ```
 
 ## Agents
@@ -40,33 +52,6 @@ Interfaces with datasets and data loaders.
 datasetio/index
 ```
 
-## Eval
-Generates outputs (via Inference or Agents) and perform scoring.
-
-```{toctree}
-:maxdepth: 1
-
-eval/index
-```
-
-## Inference
-Runs inference with an LLM.
-
-```{toctree}
-:maxdepth: 1
-
-inference/index
-```
-
-## Post Training
-Fine-tunes a model.
-
-```{toctree}
-:maxdepth: 1
-
-post_training/index
-```
-
 ## Safety
 Applies safety policies to the output at a Systems (not only model) level.
 
@@ -76,15 +61,6 @@ Applies safety policies to the output at a Systems (not only model) level.
 safety/index
 ```
 
-## Scoring
-Evaluates the outputs of the system.
-
-```{toctree}
-:maxdepth: 1
-
-scoring/index
-```
-
 ## Telemetry
 Collects telemetry data from the system.
 
@@ -94,15 +70,6 @@ Collects telemetry data from the system.
 telemetry/index
 ```
 
-## Tool Runtime
-Is associated with the ToolGroup resouces.
-
-```{toctree}
-:maxdepth: 1
-
-tool_runtime/index
-```
-
 ## Vector IO
 
 Vector IO refers to operations on vector databases, such as adding documents, searching, and deleting documents.
@@ -114,3 +81,12 @@ io and database are used to store and retrieve documents for retrieval.
 
 vector_io/index
 ```
+
+## Tool Runtime
+Is associated with the ToolGroup resources.
+
+```{toctree}
+:maxdepth: 1
+
+tool_runtime/index
+```