The SDK split the HTTP server scaffolding into the new
checker-sdk-go/checker/server subpackage. Update main.go to import
server and call server.New, and isolate the interactive form code
behind the standalone build tag so plugin/builtin builds skip
net/http entirely.
Add Chain []CertInfo to TLSProbe, carrying per-cert DER and precomputed
TLSA hashes (Cert/SPKI, SHA-256/SHA-512) plus the raw SPKI DER. This
lets downstream checkers (checker-dane) perform TLSA matching against
the observed chain without re-running a TLS handshake.
