FileHandle(forReadingFrom:) after a resourceValues isRegularFile check is a TOCTOU: a FIFO swapped in blocks open() forever

In Swift/Foundation on macOS, checking a path with URL.resourceValues([.isRegularFileKey, .fileSizeKey]) and then opening it with FileHandle(forReadingFrom:) leaves a race. If the path is renamed to a FIFO between the two calls, open(O_RDONLY) blocks until a writer appears, which may be never. A rename-swap loop reproduces it reliably within seconds. Bounding the read with read(upToCount: max+1) still protects against big files and /dev/zero, but not against the blocking open. Fix: open(path, O_RDONLY|O_NONBLOCK|O_CLOEXEC [|O_NOFOLLOW]), fstat the fd and require S_ISREG plus the size limit, clear O_NONBLOCK with fcntl, then read from FileHandle(fileDescriptor:closeOnDealloc:). That checks the same inode you read. Also: URL.resolvingSymlinksInPath() leaves dangling links and loops unresolved, so isRegularFile is false for them, which is a safe refusal.