feat: libc - add SYS_GETCHAR_NB and a non-blocking stdin readiness probe

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01NQRTGoYgnZQsh7uCh6Jsxm

programs/include/libc/montauk.h

@@ -189,6 +189,7 @@ extern "C" {
 #define MTK_SYS_WIFI_RESULTS       163
 #define MTK_SYS_WIFI_CONNECT_ASYNC 164
 #define MTK_SYS_NETIFS             165
+#define MTK_SYS_GETCHAR_NB         166
 /* @SYSCALLS-END */
 
 #define MTK_SOCK_TCP 1

programs/include/libc/stdio.h

@@ -95,6 +95,17 @@ int    ungetc(int c, FILE *stream);
 char  *fgets(char *s, int size, FILE *stream);
 int    fputs(const char *s, FILE *stream);
 
+/* MontaukOS extension: non-blocking readiness probe for stdin.
+   Returns 1 when a complete line is buffered, so a following fgets/fgetc on
+   stdin returns without blocking; 0 otherwise. Partially typed input is kept.
+   This is what a select()-style poll over stdin has to be built on -- stdio
+   descriptors are not waitable kernel objects. */
+int    montauk_stdin_ready(void);
+
+/* Blocks until a complete line is buffered on stdin, then returns 1. Same
+   buffer as montauk_stdin_ready(); nothing is consumed either way. */
+int    montauk_stdin_wait(void);
+
 void   perror(const char *s);
 FILE  *tmpfile(void);
 char  *tmpnam(char *s);