collectThreadReplies walked the parent_id tree depth-first, so an agent
reply forced to nest under its trigger comment rendered before earlier
sibling replies (A-D-B-C instead of A-B-C-D) whenever the agent returned
late. Sort the collected subtree by created_at (id tie-break) so the
thread reads in arrival order — the same order the server already feeds
agents via `comment list --thread` (ListThreadCommentsForIssue).
All other consumers of the array (resolution derivation, fold bars,
counts, deep-link) are order-independent.
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
