Create readme.txt

[Rnen-arch]

lru_cache/
├── client/
│ ├── lru_cache_proxy.h
│ ├── lru_cache_proxy.cc
│ ├── http_sse_proxy.h
│ └── http_sse_proxy.cc
├── server/
│ ├── lru_cache.h # LRU核心逻辑
│ ├── lru_cache.cc
│ ├── lru_cache_service.h # tRPC服务定义
│ ├── lru_cache_service.cc
│ └── service.hh # 生成的pb服务头
├── proto/
│ └── lru_cache.proto # protobuf定义
├── test/
│ ├── lru_cache_test.cc # 单元测试
│ └── benchmark.cc # 性能测试
├── BUILD
└── run.sh

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