Fix enable report host for entire:// mirror origins

cleanRemoteURLForReport rebuilt the reported URL from info.Host, which for an entire://cluster/gh/owner/repo origin (an already-mirrored repo) is the Entire cluster host, not github.com — so the backend got https://aws-us-east-2.entire.io/owner/repo.git and enable reporting silently failed for mirrored repos.

Add Info.CanonicalHost() to the gitremote package, derived from the existing hostToForge map, which maps the forge prefix back to its real host (gh -> github.com) and falls back to Host for unknown forges (self-hosted enterprise). Use it when building the reported URL.