♻️ Rename SocketmapAdapter to LookupServer and use generic TCP server

Rename adapter.go to lookup.go and SocketmapAdapter to LookupServer to
better reflect the component's purpose. Migrate from the socketmap-specific
server.go to the generic TCPServerConfig/StartTCPServer infrastructure,
adding context propagation to HandleConnection.

- Rename SocketmapAdapter → LookupServer, NewSocketmapAdapter → NewLookupServer
- Add StartLookupServer using TCPServerConfig with metrics callbacks
- Extract processRequest method to fix context leak (defer cancel per request)
- Move connection close responsibility to tcpserver.go
- Replace adapter_test.go + server_test.go with comprehensive lookup_test.go
- Update main.go to use new naming

Co-Authored-By: OpenCode <noreply@opencode.ai>

Author: 0x46616c6b