asymon

perf: zero-alloc hot path, bufio TCP reads, TCP_NODELAY, per-session rand

fix: remove DF flag, randomize IP ID and src port per spoofed packet

fix: compute UDP checksum on spoofed packets

docs: update README for dual-socket client, add flags table and VLESS+KCP example

fix: split client into two UDP sockets for local app and downlink recv