[undont]

Summary

• the pr overview gains write features: ga is a standard comment on the pr, gp/gq both answer
  the comment/thread under the cursor, but gq (and v_gq for visual mode) quote from the respective
  comment/thread
• also in the overview, gc now shows or hides a thread's replies
• new post_issue_comment sidecar method over graphql addComment
• ui.overview records a node id per thread and a row span per rendered comment
• a reply drops the cached thread list first: it is memoised per ttl window, so the re-opened page
  would otherwise still show the pre-reply thread
• the page wraps on a word, and indents a continuation per line via
  breakindentopt=list:-1 and formatlistpat, which reads a lot better
• a thread's footer drops the reply count once the replies are on screen, a more friendly UX
• gc in the diff released its override only on teardown, opting a thread out of
  peeking for the session with no way back; it now lapses as soon as the cursor leaves the anchor
• thread_collapsed read the configured display mode rather than the one a split layout
  forces, so expanded plus split kept the same stuck override
• ui.compose lands the cursor past a prefill, which also fixes the conflict re-prompt
  putting you above your own body

Test plan

• make check and make gql-validate both clean