[Diffusion] Support LoRA in step-wise execution (#3639)

Signed-off-by: samithuang <285365963@qq.com>

docs/user_guide/diffusion/step_execution.md

@@ -60,6 +60,9 @@ batching only becomes relevant when `--max-num-seqs > 1`.
 - `cache_backend` is not supported together with step execution.
 - Unsupported pipelines fail early during model loading.
 - Request-mode extras such as KV transfer are not wired into step mode yet.
+- LoRA is supported in step mode, but each batch must use a single adapter:
+  requests with different `lora_request` or `lora_scale` are scheduled into
+  separate batches.
 
 ## When To Use It
 

docs/user_guide/diffusion_features.md

@@ -184,7 +184,7 @@ The following tables show which models support each feature:
 | **💾VAE Patch Parallel** | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | | | |
 | **💾FP8 Quant** | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❓ | ❓ | ✅ | ✅ | ✅ | | | |
 | **🔧LoRA Inference** | ❓ | ❓ | ❓ | ❓ | ❓ | ❓ | ❓ | ❓ | ❓ | ❓ | ❓ | ❓ | | |
-| **🔄Step Execution** | ❌ | ❌ | ✅ | ✅ | ✅ | ✅ | ❓ | ❓ | ✅ | ❓ | ✅ | ✅ | ❌ | |
+| **🔄Step Execution** | ❌ | ❌ | ✅ | ✅ | ✅ | ✅ | ❓ | ❓ | ✅ | ❓ | ✅ | ✅ | ✅ | |
 
 !!! info
 
@@ -193,7 +193,7 @@ The following tables show which models support each feature:
     3. CPU Offloading (Layerwise) and CPU Offloading (Module-wise) are not compatible.
     4. CPU Offloading (Layerwise) supports single-card for now.
     5. Using FP8-Quant as an example of qunatization methods.
-    6. Step Execution is not compatible with cache backends (TeaCache, Cache-DiT) or LoRA.
+    6. Step Execution is not compatible with cache backends (TeaCache, Cache-DiT). LoRA is supported, but each scheduled batch must use a single adapter (requests with different `lora_request` or `lora_scale` are kept in separate batches).
 
 
 ## Multi-Thread Weight Loading