perejaslav/cpdown ? reverse-engineered prompt

Build me a lightweight Chrome extension called cpdown that turns useful web content into clean Markdown I can copy or save as an .md file. I want it to work from the toolbar button and a keyboard shortcut, and it should handle normal article pages by stripping out clutter and keeping the readable content.

It also needs special flows for YouTube and X. On YouTube, if I am on a video page, clicking the extension should grab the transcript reliably and show a small toast with the estimated token count plus Copy and Save .md actions. I also want a right click option on YouTube links that opens the video in the background, pulls the subtitles, then shows the result on the page I was on. For X, add a right click option that copies visible posts, threads, or article style pages as Markdown from the open page, without using the official API.

Make the feedback UI consistent, simple, and dark mode aware. Look up current browser extension docs if you need to.