Adds socket_setsockopt(conn_id, level, optname, optval, optlen) — a runtime passthrough to Linux setsockopt for TCP/UDP socket connections, deliberately skipping any YAML option-name mapping layer. The feature threads cleanly through the existing Engine vtable, with a NOT_SUPPORTED base-class default so non-socket engines require no changes.

• C++ API (include/daqiri/common.h, src/common.cpp, src/engine.h/cpp): New public free-function dispatches via g_daqiri_engine->socket_setsockopt(); base class logs CRITICAL and returns NOT_SUPPORTED for engines that don't implement it.
• Socket engine (src/engines/socket/daqiri_socket_engine.cpp): Full implementation with RoCE guard, null-optval check, shared_ptr connection lookup under state_mutex_, and ::setsockopt passthrough. A new private helper apply_socket_int_option consolidates the repeated int-valued setup calls (SO_REUSEADDR, TCP_NODELAY) that previously used bare ::setsockopt with silently ignored return values.
• Python bindings (python/daqiri_common_pybind.cpp): Shim dispatches bool, int, str, bytes, and buffer-protocol objects; GIL is released before each C call and reacquired (via RAII) before any Python-heap cleanup, preserving correct destruction order.
• Docs (AGENTS.md, README.md, all relevant docs/): Updated across every doc-sync target.