A single comment on a line outside a diff hunk 422s the whole review on
GitHub, which the 422/500 fallback (ported here from the Forgejo work,
including payload shaping and commit_id) then degraded into plain issue
comments. Now we fetch /pulls/{n}/files, compute per-hunk anchorable line
sets, drop non-anchorable comments, fold them into the review summary, and
only fall back to issue comments for genuine 422/500s that survive
filtering. Files-fetch failure fails open (submit unfiltered).
djdembeck
71d608aae6