0.28.1 — Robust Global Auto-Updater

Fixed: Global package manager auto-update commands — updated checkForUpdate() and cmdUpdate() to run pnpm add -g kandown@latest (instead of pnpm install -g kandown), with fallback chain across pnpm, npm, yarn, and bun.
Fixed: kandown update command behavior — kandown update now queries the npm registry for the latest release, updates the global CLI package using the active package manager, and refreshes project .kandown/kandown.html files.
Fixed: Terminal & tmux auto-update compatibility — fixed checkForUpdate() invocation so interactive terminal sessions (including tmux and iTerm) automatically detect and offer updates.