Lint reports now show what they graded from

Grades for a bare repo URL could differ between runs: the linter reads GitHub Releases via the API (up to 100 releases) but falls back to the public releases feed (~10 latest) when the shared API quota is exhausted — same repo, different sample, different grade.

Every lint report (web, JSON graded_from, and format=text) now says exactly which source it graded: GitHub/GitLab/Codeberg Releases API, GitHub recent-releases feed (with a note that the API was rate-limited), RSS/Atom feed, or the raw file. Repo-URL reports also note that grades can vary and that a raw CHANGELOG.md URL gives a stable grade.