Hwaro::Services::CharsetHandler

HTTP::StaticFileHandler derives Content-Type from the file extension via MIME.from_extension and writes it without a charset parameter — so robots.txt / llms.txt / sitemap and search index responses all advertise no charset, leaving UTF-8 bytes (e.g. Korean LLM-instructions) at the mercy of client-side heuristics. This handler runs after the static handler and appends ; charset=utf-8 to text-shaped responses.

We only touch types we know are text. Binary types (image/png, font/woff2, etc.) are left alone — adding a charset there would be wrong, not just useless. image/svg+xml is treated as text because it's XML.