Not long time ago I started making a note taking thing and some of your goals align with mine - minimal, keep your data local. What is different about my thing besides being very crude (EasyMDE and a few CGI programs in C served by BusyBox httpd) is the goal of using it as my new tab on devices to cut down on using tabs as bookmarks.

I see myself adopting your solution for my case or maybe extending it. What I'm missing: image support and ToC.