fix: ramdisk Open no longer opens directory entries

SYS_OPEN succeeded on directory tar entries, so userspace stat() -
which tries open-as-file first - reported every directory as a
regular file. GCC's include-path setup stats each search directory
and rejected all the real ones with "not a directory" warnings.
Directories now fall through Open to -1 and stat() classifies them
via the (recently fixed) ReadDir existence probe.

Co-Authored-By: Claude Fable 5 <[email protected]>

kernel/src/Api/BuildNo.hpp

@@ -12,4 +12,4 @@
 
 #pragma once
 
-#define MONTAUK_BUILD_NUMBER 20
+#define MONTAUK_BUILD_NUMBER 21

kernel/src/Fs/Ramdisk.cpp

@@ -175,6 +175,13 @@ namespace Fs::Ramdisk {
         if (path[0] == '/') path++;
 
         for (int i = 0; i < fileCount; i++) {
+            // Directories are not openable as files. Without this,
+            // userspace stat() classified every directory with a tar
+            // entry as a regular file (GCC's include-path setup then
+            // rejected real directories with "not a directory").
+            if (fileTable[i].isDirectory) {
+                continue;
+            }
             if (StrEqual(fileTable[i].name, path)) {
                 return i;
             }