feat: add is_terminal_attached syscall

programs/include/Api/Syscall.hpp

@@ -240,6 +240,7 @@ namespace montauk::abi {
     static constexpr uint64_t SYS_SPAWN_ENV           = 173;
 
     static constexpr uint64_t SYS_LOG_WRITE           = 176;  // (logMessage) -> 0
+    static constexpr uint64_t SYS_TERMINAL_ATTACHED   = 177;  // () -> 1 when connected to a userspace terminal
 
     // Tunable parameters (for SYS_SDR_SETPARAM / SYS_SDR_GETPARAM).
     static constexpr int SDR_PARAM_FREQ        = 0;  // center frequency, Hz