feat: add is_terminal_attached syscall

template/docs/syscalls.md

@@ -32,6 +32,7 @@ void     exit(int code);                              // Terminate process (nore
 void     yield();                                     // Yield CPU to scheduler
 void     sleep_ms(uint64_t ms);                       // Sleep for milliseconds
 int      getpid();                                    // Get current process ID
+bool     terminal_attached();                         // Whether stdout is connected to a userspace terminal
 int      spawn(const char* path, const char* args);   // Spawn child, inheriting environment
 int      waitpid(int pid);                            // Wait for process to exit
 int      kill(int pid);                               // Kill a process