Conflicts, part 3: one tap has the crew propose the resolution as a commit on the pull's branch #1968

Split from #1134.

Done looks like:

• [ ] "Have the crew propose" on the conflicts page (same-origin POST, write access) starts one run on the pull's own branch whose brief carries the conflict: both sides' commits since the base, the files and blocks, and the tests that cover them.
• [ ] The resolution comes back as a commit on the branch with a note on the pull saying what it chose and why; the conflicts page then shows it, and the person can edit it there.
• [ ] Test with the stand-in Claude Code: the proposal lands as a commit on the head branch and the note is on the pull.

Start from today's main, at or after 36daece8. The red 'the release record is newest first' on earlier tries was main's own fault (#1837, fixed in 39e98bc9), not the builder's. A new migration is a file src/core/migrations/<UTC yyyymmddHHMMSS>-<name>.ts (see 20261015230000-a-domain-drill.ts), never a number; do not hand-edit src/core/releases.json. Before pushing run bun x tsc --noEmit, the tests this touches, the schema-migrations and schema-additive tests if you add a migration, and test/check-list.test.ts; name every new test file in GATE in scripts/gate.ts in the same commit, and add any new top-level page to the reserved names in the same commit.

Parked by the crew: the check failed ("the crew proposes a resolution > one tap lands a commit on the head branch and a note on the pull") and the decider saw no point in another try (pull #2031 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.