supportClipboard
Clipboard write that also works off a non-secure origin.
navigator.clipboard only exists in a secure context (HTTPS / localhost).
Over plain HTTP - a LAN IP, a ZeroTier address, a port-forwarded dev host -
it is undefined, so a copy button wired straight to it silently does
nothing. copyText falls back to a hidden <textarea> +
document.execCommand("copy"), which is deprecated but still the only thing
that works there.