feat: add cwd tracking to kernel, remove shell hack, update system utilities to use getcwd, fix tcc libc stub, fix nonexistent directory issue

programs/include/libc/montauk.h

@@ -97,6 +97,8 @@ extern "C" {
 #define MTK_SYS_AUDIOCTL        83
 #define MTK_SYS_SETTZ           90
 #define MTK_SYS_GETTZ           91
+#define MTK_SYS_GETCWD          95
+#define MTK_SYS_CHDIR           96
 
 #define MTK_SOCK_TCP 1
 #define MTK_SOCK_UDP 2
@@ -318,6 +320,14 @@ static inline int mtk_getargs(char *buf, unsigned long max_len) {
     return (int)_mtk_syscall2(MTK_SYS_GETARGS, (long)buf, (long)max_len);
 }
 
+static inline int mtk_chdir(const char *path) {
+    return (int)_mtk_syscall1(MTK_SYS_CHDIR, (long)path);
+}
+
+static inline int mtk_getcwd(char *buf, unsigned long max_len) {
+    return (int)_mtk_syscall2(MTK_SYS_GETCWD, (long)buf, (long)max_len);
+}
+
 /* ====================================================================
    Console I/O
    ==================================================================== */

programs/include/libc/unistd.h

@@ -13,6 +13,8 @@ int    read(int fd, void *buf, size_t count);
 int    write(int fd, const void *buf, size_t count);
 int    close(int fd);
 long   lseek(int fd, long offset, int whence);
+int    chdir(const char *path);
+char  *getcwd(char *buf, size_t size);
 
 unsigned int sleep(unsigned int seconds);