Image size measurement is remembered instead of repeated

When Claude Code estimates how much is in a conversation, it measures each image's size in bytes and pixels. It used to work this out from the image data every time. It now remembers the result for each image. If its first attempt to read an image's header (the start of the file that describes it) fails, it tries again with a longer piece of the file. The length of what Claude sends to its tools is also remembered in the same way.