add Chinese annotations to all source files for learning purposes

Annotated 16 source files covering the full architecture:
engine (scheduler, block manager, model runner), layers (attention,
linear, sampler, etc.), model (qwen3), and utils.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

nanovllm/utils/loader.py

@@ -6,23 +6,38 @@ from safetensors import safe_open
 
 
 def default_weight_loader(param: nn.Parameter, loaded_weight: torch.Tensor):
+    """默认权重加载器：直接将加载的权重拷贝到参数中。"""
     param.data.copy_(loaded_weight)
 
 
 def load_model(model: nn.Module, path: str):
+    """从 HuggingFace safetensors 格式加载模型权重。
+
+    支持融合模块的权重加载：本项目将 Q/K/V 投影融合为 qkv_proj，
+    将 gate/up 投影融合为 gate_up_proj。加载时需要通过 packed_modules_mapping
+    将原始的独立权重名映射到融合后的模块，并使用自定义的 weight_loader
+    将权重放置到正确位置。
+
+    Args:
+        model: 要加载权重的模型。
+        path: 模型目录路径，包含 .safetensors 文件。
+    """
     packed_modules_mapping = getattr(model, "packed_modules_mapping", {})
     for file in glob(os.path.join(path, "*.safetensors")):
         with safe_open(file, "pt", "cpu") as f:
             for weight_name in f.keys():
+                # 检查是否为融合模块的子权重（如 q_proj, k_proj, gate_proj 等）
                 for k in packed_modules_mapping:
                     if k in weight_name:
                         v, shard_id = packed_modules_mapping[k]
+                        # 替换权重名：如 "model.layers.0.self_attn.q_proj.weight" → "...qkv_proj.weight"
                         param_name = weight_name.replace(k, v)
                         param = model.get_parameter(param_name)
                         weight_loader = getattr(param, "weight_loader")
                         weight_loader(param, f.get_tensor(weight_name), shard_id)
                         break
                 else:
+                    # 普通权重：直接加载
                     param = model.get_parameter(weight_name)
                     weight_loader = getattr(param, "weight_loader", default_weight_loader)
                     weight_loader(param, f.get_tensor(weight_name))