Added #ifdef __cplusplus / extern "C" { ... } / #endif to ~65 headers in src/ and lib/, enabling the C library to be linked into C++ code (chatgui). Fixed packet_dump.h (added missing header guard) and etcp_bbr.h (#pragma once guard).
- secure_channel: add sc_stream_state + sc_stream_init/sc_stream_xor/sc_stream_cleanup AES-128-CTR streaming cipher for incremental encrypt/decrypt - stcp.h/c: shared stcp_conn lifecycle, set_on_close, rx/tx queue setup - stcp_server: listen/accept, handshake (obfuscated pubkey + ECDH + stream), DATA phase - stcp_client: connect, handshake, DATA phase - Protocol: key_block(72) + enc(data+crc) + padding for handshake size(2 LE) + enc(data+crc) for data messages - Tests: test_stream_cipher (AES-CTR correctness) test_stcp (6 cases: sizes 0..65535, 200 msgs, wrong key, close detection, multi-client, interleaved send/recv) - Fix: 0-length message handling in tx_queue callbacks
Evgeny