Sunset-header checker

RFC 8594 lets any API or site declare its end-of-life in a machine- readable Sunset header. Paste a URL - we check whether it does. Public URLs only, one polite fetch, robots.txt honored.

Vendors: adding a Sunset header is one line. Spec: RFC 8594. Track what does not declare itself: check your stack. Shutdown Watch tracks vendor announcements and public deadlines; it is monitoring assistance, not legal or migration advice.