Add a developer-guide page for running the Ink TUI and Electron desktop
app from a git worktree without a full npm install per checkout, via the
htui/hgui shell helpers that share node_modules from a canonical deps
checkout by symlink (falling back to a local npm ci when the lockfile
diverges). Registers it in the sidebar, cross-links from the TUI and git
-worktrees pages, and documents the previously-undocumented
HERMES_DESKTOP_PYTHON / HERMES_DESKTOP_DEV_SERVER env vars the desktop
backend reads.
