[diffusion] docs: consolidate diffusion documentation into docs (#18095)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
Co-authored-by: JiaxinD <djx2048@gmail.com>

docs/index.rst

@@ -74,11 +74,30 @@ Its core features include:
    :caption: Supported Models
 
    supported_models/text_generation/index
-   supported_models/image_generation/index
    supported_models/retrieval_ranking/index
    supported_models/specialized/index
    supported_models/extending/index
 
+.. toctree::
+   :maxdepth: 2
+   :caption: SGLang Diffusion
+
+   diffusion/index
+   diffusion/installation
+   diffusion/compatibility_matrix
+   diffusion/api/cli
+   diffusion/api/openai_api
+   diffusion/performance/index
+   diffusion/performance/attention_backends
+   diffusion/performance/profiling
+   diffusion/performance/cache/index
+   diffusion/performance/cache/cache_dit
+   diffusion/performance/cache/teacache
+   diffusion/support_new_models
+   diffusion/contributing
+   diffusion/ci_perf
+   diffusion/environment_variables
+
 .. toctree::
    :maxdepth: 1
    :caption: Hardware Platforms