[docs] update adding models docs (#563)

Signed-off-by: hsliu <liuhongsheng4@huawei.com>

docs/.nav.yml

@@ -40,7 +40,7 @@ nav:
       flatten_single_child_sections: true
   - Model Implementation:
     - contributing/model/README.md
-    - contributing/model/adding_multi_stage_model.md
+    - contributing/model/adding_omni_model.md
     - contributing/model/adding_diffusion_model.md
   - CI: contributing/ci
   - Tests: contributing/tests

docs/contributing/model/README.md

@@ -4,26 +4,12 @@ This section provides comprehensive guidance on how to add a new model to vLLM-O
 
 ## Documentation
 
-- **[Adding a New Omni Model Guide](adding_multi_stage_model.md)**: Complete step-by-step guide using Qwen3-Omni as an example
+- **[Adding an Omni-Modality Model](adding_omni_model.md)**: Complete step-by-step guide using Qwen3-Omni as an example.
 
-The guide covers:
-- Directory structure and organization
-- Implementing stage components (thinker, talker, code2wav)
-- Creating the unified model class
-- Model registration
-- Stage configuration
-- Stage input processors
-- Testing strategies
-
-- **[Adding a New Diffusion Model Guide](adding_diffusion_model.md)**: Complete step-by-step guide using Qwen/Qwen-Image-Edit as an example
-The guide covers:
-- Overview
-- Directory Structure
-- Step-by-Step Implementation
-- Testing
+- **[Adding a Diffusion Model](adding_diffusion_model.md)**: Complete step-by-step guide using Qwen/Qwen-Image-Edit as an example.
 
 
 
 ## Quick Start
 
-For a quick reference, see the [Adding a New Multi-Stage Model Guide](adding_multi_stage_model.md) and [Adding a New Diffusion Model Guide](adding_diffusion_model.md).
+For a quick reference, see the [Adding a New Multi-Stage Model Guide](adding_omni_model.md) and [Adding a New Diffusion Model Guide](adding_diffusion_model.md).

docs/contributing/model/adding_omni_model.md

@@ -1,4 +1,4 @@
-# Adding a Multi-Stage Model
+# Adding an Omni-Modality Model
 
 This guide walks through the process of adding a new multi-stage model to vLLM-Omni, using **Qwen3-Omni** as a comprehensive example. Qwen3-Omni is a multi-stage omni-modality model that demonstrates the full capabilities of vLLM-Omni's architecture.