[Refactor] Remove legacy --stage-configs-path from the serve CLI (#5647)

Signed-off-by: zwhzzz0821 <2831474076@qq.com>

docs/contributing/model/adding_diffusion_model.md

@@ -653,7 +653,7 @@ python end2end.py --model your-org/your-model-name --modality text2img --prompts
 Mirror BAGEL’s online serving setup:
 
 - Server launcher: `examples/online_serving/your_model_name/run_server.sh`
-  - Wrap `vllm serve ... --omni --port ...` (and `--stage-configs-path ...` if needed)
+  - Wrap `vllm serve ... --omni --port ...` (and `--deploy-config ...` if needed)
 - Client: `examples/online_serving/your_model_name/openai_chat_client.py`
   - Send requests to `POST /v1/chat/completions`
   - Support multimodal inputs (e.g., base64 image) if your model needs it

docs/contributing/model/adding_omni_model.md

@@ -48,8 +48,8 @@ vllm_omni/deploy/
 ```
 
 New in-tree models should register their `PipelineConfig` in
-`vllm_omni/config/pipeline_registry.py`; use `--stage-configs-path` only for
-custom legacy `stage_args` YAMLs.
+`vllm_omni/config/pipeline_registry.py`; use `--deploy-config` for custom
+deployment YAMLs.
 
 ## Step-by-Step Implementation
 

docs/contributing/model/adding_tts_model.md

@@ -449,9 +449,8 @@ Key configuration fields:
 !!! note
     New in-tree models should define frozen topology in `models/<model>/pipeline.py`,
     register it in `vllm_omni/config/pipeline_registry.py`, and put deployment
-    knobs in `vllm_omni/deploy/<model>.yaml`. Legacy `stage_args` YAMLs are still
-    accepted for custom configs via `--stage-configs-path`, but should not be used
-    for new bundled defaults.
+    knobs in `vllm_omni/deploy/<model>.yaml`. Use `--deploy-config` to load a
+    custom deployment YAML.
 
 ### Batch mode