fix: reject opening directories as files in ext2 and fat32, add mbrtowc to libc

kernel/src/Api/BuildNo.hpp

@@ -12,4 +12,4 @@
 
 #pragma once
 
-#define MONTAUK_BUILD_NUMBER 182
+#define MONTAUK_BUILD_NUMBER 184

kernel/src/Fs/Ext2.cpp

@@ -1202,6 +1202,13 @@ namespace Fs::Ext2 {
         Inode inode;
         if (!TraversePath(self, path, &inodeNum, &inode)) return -1;
 
+        // Directories are not openable as files, matching the ramdisk. A
+        // handle on one would fail every read/write anyway, and userspace
+        // stat() falls back to open() when it cannot get real metadata:
+        // succeeding here classified every directory as a regular file and
+        // GCC's include-path setup then rejected them as "not a directory".
+        if ((inode.i_mode & IMODE_TYPE_MASK) == IMODE_DIR) return -1;
+
         for (int i = 0; i < MaxFilesPerInstance; i++) {
             if (!self.files[i].inUse) {
                 self.files[i].inUse = true;

kernel/src/Fs/Fat32.cpp

@@ -955,6 +955,10 @@ namespace Fs::Fat32 {
         ParsedEntry entry;
         if (!TraversePath(inst, path, &entry)) return -1;
 
+        // Directories are not openable as files; see the matching note in
+        // Ext2::OpenImpl (userspace stat() falls back to open()).
+        if ((entry.attributes & ATTR_DIRECTORY) != 0) return -1;
+
         // Find a free file handle
         auto& self = g_instances[inst];
         for (int i = 0; i < MaxFilesPerInstance; i++) {