Paste an image into a post -- that is the whole feature

Copy a screenshot or an image file to the clipboard, click into the composer, paste: a small "Uploading image..." note appears at the cursor and a moment later the picture takes its place, sized to fit the column. Publish it and the image is part of the post, served from your server like everything else you write. It works like Slack and GitHub -- no Upload command, no dialog, nothing to learn. The limit is 2MB per image; paste something bigger and a dialog says so. The Publish button waits politely until every pasted image has finished uploading, so a post can never go out with a half-arrived picture. Rich-text mode only for now -- markdown mode will get the same feature, inserting the image reference as text, over the same plumbing. First image posts in the wild: demo 227 and 228 ("We have images.") and rss.chat 378. (Theme v0.5.338, with a new uploadMedia call in api.js by DW.)