Every PR adds an entry at the top of Completed Steps in TODO.md, so each
merge to next left the other open PRs conflicting there. A root
.gitattributes, copied from sneak/prompts, marks TODO.md merge=union: two
branches that each add an entry at the same place merge without a conflict
and keep both. Git then never reports a conflict in TODO.md, so the
Workflow now says to read the merged entries after every merge or rebase.
Model: opus-5-5
