[Model] Add VoxCPM2 startup LoRA adapter support (#7108)

Signed-off-by: bezdarnost <urumbekovaman@gmail.com>
Co-authored-by: bezdarnost <urumbekovaman@gmail.com>

docs/serving/speech_api.md

@@ -777,6 +777,40 @@ hidden-state dtype before the output projection. Consequently, a float32 stage c
 | ------- | ------------- |
 | `openbmb/VoxCPM2` | TTS + voice cloning with built-in speaker presets and uploaded-voice support. Accepts `voice` (preset or uploaded) or `ref_audio` + optional `ref_text`. |
 
+#### Startup LoRA adapter
+
+To serve a fine-tuned VoxCPM2 voice, set
+`voxcpm2_runtime_config.startup_lora_path` in the stage's `hf_overrides`.
+Copy `vllm_omni/deploy/voxcpm2.yaml` to a local deploy config and add this key
+alongside its existing runtime settings:
+
+```yaml
+# Under stages[0].engine_extras.hf_overrides.voxcpm2_runtime_config:
+startup_lora_path: /absolute/path/to/adapter
+```
+
+Then launch with the modified config:
+
+```bash
+vllm serve openbmb/VoxCPM2 --omni --deploy-config /absolute/path/to/voxcpm2-lora.yaml
+```
+
+The directory must be accessible to the worker and contain the native VoxCPM2
+training export: `lora_config.json` (with a `lora_config` object containing
+`r`, `alpha`, enabled groups, and target module names) and
+`lora_weights.safetensors`. PEFT checkpoints and pickle checkpoints are not
+accepted. Missing, unexpected, non-finite, or incorrectly shaped adapter
+tensors fail model loading rather than silently loading a partial adapter.
+
+The adapter is merged into the base LM, residual LM, LocDiT, and optional
+projection layers selected by its configuration, after base weight loading
+and before compilation or CUDA graph capture. All requests use that adapter;
+`voice` still selects a reference voice, not a LoRA adapter. Changing adapters
+requires restarting the server. Runtime loading/unloading, per-request
+multi-LoRA selection, and `load_format=dummy` are not supported by this path.
+Weight fusion rounds to the base model's dtype, so numerical and speech-quality
+parity should be checked against the upstream adapter on your deployment.
+
 ### MOSS-TTS-Nano
 
 | Model | Description |