Serve mode and live reload

taragen serve is for writing:

• Pages, outputs, generated pages, and cards render when requested, from the latest source.
• Drafts are visible and included in listings.
• Aliases answer with 301; _redirects rules answer with their status.
• HTML responses get a small script that reloads the browser when anything in the site changes: pages, CSS, images, fonts, _redirects, anything outside dot-prefixed paths and _public/. Non-HTML responses (text outputs, cards, feeds) don't get the script.
• A render error shows as a 500 with the error text.
• Paths that aren't pages, outputs, aliases, or redirects are served from disk, including underscore paths like /_assets/....

After a change to a page source, a folder, _outputs/, a font, or _redirects, the whole site is re-read, so new pages, generated pages, backlinks, and aliases appear on the next reload.

Requests are rendered one at a time. That's fine for local preview; use build for production.