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/__init__.py

@@ -1,2 +1,12 @@
+# nano-vllm: 一个轻量级的 vLLM 实现
+#
+# 核心架构:
+# LLM (入口) → LLMEngine (引擎) → Scheduler (调度器) + ModelRunner (模型运行器)
+#                                      ↓                      ↓
+#                               BlockManager (KV缓存管理)    Qwen3ForCausalLM (模型)
+#
+# 数据流:
+# 用户请求 → Sequence → Scheduler 调度 → ModelRunner 准备输入 → 模型前向 → 采样 → 返回结果
+
 from nanovllm.llm import LLM
 from nanovllm.sampling_params import SamplingParams