herdr web ui v0.3.12

Added

• The website has a demo, https://devswha.github.io/herdr-web-ui/demo/: the app itself on a
  fictional session, no server. Its five panes, chats and Codex approval are the README media's;
  answering the approval, sending a message and typing into the shell pane all get demo answers.

Fixed

• Installing no longer compiles a native module. The terminal addon comes prebuilt for Linux x64
  and arm64 and for macOS (@lydell/node-pty, node-pty 1.1.0 repackaged), so a PC without Python
  and a C++ toolchain installs, where herdr plugin install used to end in a page of node-gyp
  errors and "Plugin was not installed". The first build step now says in one line what is
  missing (bun, node, or a version too old) instead of failing some steps later.