fix: make common transport handshake compile and work with RDMA

[Spicy-cream]

Summary

This PR is based on #22 and fixes the compilation and runtime issues found while validating the common transport handshake implementation with RDMA.

Fixes

• Fixed compilation errors in AdapterTransport and the handshake I/O implementation.
• Removed obsolete RDMA handshake code and unresolved conflict remnants.
• Prepared RDMA resources before negotiating the remote connection parameters.
• Fixed an invalid UpgradeActive() check that ran before RDMA activation.
• Held a valid Socket reference during the asynchronous client handshake.
• Fixed the Over dereferenced VRefId error during client shutdown.
• Preserved the protocol identifier and the main design of PR handshake 逻辑抽取transport层，由AdapterTransport统一管理handshake和升级到rdma/ubshm逻辑 #22 as much as possible.

Build Verification

The project was successfully built with:

cmake -S . -B build-rdma \
  -DCMAKE_BUILD_TYPE=Release \
  -DWITH_RDMA=ON

cmake --build build-rdma --parallel "$(nproc)"